TypeII-2 TypeII-1 TypeI-2 Olafs Simulator TypeIA-T
(since April 22, 1997)

The CURTA Calculator Page

"The world's first, last, and ONLY, mechanical handheld pocket calculator.*"

Last Update: July 29, 2022 -- THE CURTA REFERENCE

NEW: Check out the Curta 1A Prototype History

curta tn

   o The Curta Poster
Owners Registry
   o Curta Registry
Curt Herzstark
   o Curt Herzstark
   o Curt Herzstark Interview
   o Curta Backup Article
   o Miniature Machine
   o Pocket Calculators
   o The Curious History
Curta Simulators
   o Olaf Veenstra's New YACS
   o Sebastian Dammers' 3D CAD
   o Onshape 3D Curta CAD
   o 3D Printed Curta
   o Curta WiKi
   o Curta Stats
   o Curta: Oldest
   o Curta Date
   o Curta Variations
   o Curta Manual
   o Curta Dimensions & Timing
   o Curta Service Manual
   o Curta Lubrication
   o Curta Factory Drawings
   o Curta Tools
   o Curta Disassembly
   o Curta Patents
   o Jack's Curta Repair (US)
   o Hans' Curta Repair (Europe)
   o Romano's Curta Repair (Italy)
   o Curta: The Ayen Collection
   o Curta: The Pedrosa Collection
Curta Pictures
   o Nice Curta Photos
   o Curta: Ray Traced
Curta Demos
   o Curta Demos
   o Fake Demos
   o Curta: Cut & Special
   o The Curta 1A (new-7/16/22)
   o Curta Prototypes
Curta Literature
   o Curta Ads
   o Curta Articles
   o Curta News Letters
   o Curta Literature
Curta Other
   o Curta Pins
   o Curta Museums & School
   o Curta: Media
        - Books
        - Stamp
        - Audio
        - Video
Curta Links
   o Curta Links



(Click here)

(Click here)

Introducing the classic Curta Calculator poster for all Curta fans. This fabulous poster shows a detailed layout of the inner working of Curt Herzstark's amazing machine. All Curta parts are close to actual size and displayed in multiple exploded views. Every part is labeled with its original name as designated in the Contina A.G. factory service manual. The elaborate and detailed poster design was nearly a year in planning and execution. Original factory photographs, drawings and artwork have been combined with new imagery to produce this engineer's view of a mechanical masterpiece. Many thanks are due to Carl and Jack for their encouragement and enthusiasm.

The Curta Calculator poster is very suitable for framing and will make a wonderful gift to any Curta enthusiast. It is an essential element in any Curta collection.

The poster measures 24 1/2" (62cm) in width and 16" (41cm) in height and is printed on high quality Strobe Gloss 100# cover paper. The poster will be shipped in a rugged 3" x 18" Kraft Mailing tube.



(Click here)

The Curta Calculator poster printed in the German words of the Great Master, Curt Herzstark.

Introducing the classic Curta Calculator poster in German. Like the original Curta poster, this fabulous poster shows a detailed layout of the inner working of Curt Herzstark's amazing machine. All Curta parts are close to actual size and displayed in multiple exploded views. Every part is labeled with its original name as designated in the Contina A.G. factory service manual. The elaborate and detailed poster design was nearly a year in planning and execution. Original factory photographs, drawings and artwork have been combined with new imagery to produce this engineer's view of a mechanical masterpiece. Many thanks are due to Hans-Rudolf Roshard for his help translating this poster to German.

The Curta German Calculator poster is very suitable for framing and will make a wonderful gift to any Curta enthusiast. It is an essential element in any Curta collection.

The poster measures 24 1/2" (62cm) in width and 16" (41cm) in height and is printed on high quality Strobe Gloss 100# cover paper. The poster will be shipped in a rugged 3" x 18" Kraft Mailing tube.

(Click here)

Buyer Feedback!

  • The poster arrived yesterday and it's terrific!   You did a really great job on it and I'd think any Curta collector will want one too.   What a great idea you had and thanks again so much for creating it. -- Greg -- Hillsboro, Oregon   USA

  • The poster was received today in perfect condition.   I thank you for your prompt and friendly service.   I'll be framing it and hanging it in my den. -- Jim -- Beachwood, Ohio   USA

  • Thanks!   This will hang in my office at NASA.   I have a Curta that I inherited from my great Uncle. -- Donald -- Huntsville, Alabama   USA

  • I received it a couple of days ago... Thank you!   It's wonderful!   Now I just have to find a frame and it will hang in pride of place in my house. -- Cath -- Bedfordshire, United Kingdom

  • Your wonderful Curta poster arrived well yesterday.   Thanks and best regards from Germany. -- Hermann -- Bayern, Germany

  • I have received the wonderful curta poster and I am inspired.   I congratulate you too this excellent poster. -- Bernd -- Langerwehe-Schlich, Germany

  • I received the Curta poster and it is beautiful to my eyes.   Even the sturdy custom mailing tube is a keeper.   I have the poster displayed temporarily in a poster frame with a thin plastic cover until I have a permanent frame made for it. -- Robert -- Alpine, Texas   USA

  • Hi Rick.   Just a quick note to let you know the Curta poster arrived today.   I am VERY pleased with it and plan to frame it for my office.   Thanks again! -- Sam -- Ridgecrest, California   USA

  • Rick - the Curta poster is absolutely fabulous, both the production quality and the concept.   It's something NO Curta Home should be without. -- Skip Godfrey -- Billings Montana   USA

  • Hi Rick, thanks a lot, I just received the poster!   It is fantastic, really well done.   Greetings from Madrid, Spain -- Angela

  • Speedy, secure shipment of an excellent product.   Great gift!   Thanks.   A+++ -- Bruce -- Okemos, Michigan   USA

  • The Curta poster is great.   I'm very pleased.   Sent quickly, too.   Thanks! -- Paul -- Hartland, Michigan   USA

  • Really beautiful item.   Really fast ship.   Thanks for a perfect transaction!! -- Kerry -- Sayre, Pennsylvania   USA

  • Excellent item, fast ship and well packed A+++++ -- Brian -- Lawrence, Kansas   USA

  • Thanks for the poster that I just bought.   It is great. -- Mark -- Santa Clara, CA   USA

  • Hi Rick, Received the poster today.   BEAUTIFUL!!!!   I left very positive feedback.   Thanks again -- Tom -- Stoughton, Wisconsin   USA

  • Hi Rick -- Beautiful job on the poster!   'twill be framed soon. -- Larry in Springboro, OH   USA

  • The Curta poster is wonderful!  Thanks so much.   --   Pam - Tucson, AZ  USA

  • Hi Rick, The poster arrived today it's fantastic!  Absolutely beautiful!  Thanks, Bob - Palo Alto, CA  USA

  • Rick, Your work is outstanding!  The poster is amazing; I've been studying it since it arrived.  The detail and quality of the photos is excellent and the amount of data you have included is impressive.  I noticed your name in the CURTA article in the January [2004] Scientific American (in the box on page 98 where the author, Cliff Stoll, thanks his elves) and now I know the source of some of the photos in the article since I visited your web site. -- Charlie -- Randallstown, MD   USA

  • Rick, I got the poster and my engineer colleagues come to my office just to study it!  Ray - North Bend, WA  USA

Countries Sold To (so far)

  • AE - United Arab Emirates
  • AR - Argentina
  • AT - Austria
  • AU - Australia
  • BE - Belgium
  • BR - Brazil
  • CA - Canada
  • CH - Switzerland
  • CL - Chile
  • CN - China
  • CO - Colombia
  • CY - Cyprus
  • CZ - Czech Republic
  • DE - Germany
  • DK - Denmark
  • DM - Dominica
  • EC - Ecuador
  • ES - Spain
  • FI - Finland
  • FR - France
  • GB - United Kingdom
  • GP - Guadeloupe
  • GR - Greece
  • HK - Hong kong
  • HN - Honduras
  • HU - Hungary
  • IE - Ireland
  • IL - Israel
  • IN - India
  • IR - Iran
  • IT - Italy
  • JP - Japan
  • KR - South Korea
  • LI - Liechtenstein
  • LU - Luxembourg
  • MN - Mongolia
  • MX - Mexico
  • NE - Niger
  • NI - Nicaragua
  • NL - Netherlands
  • NO - Norway
  • NZ - New Zealand
  • PH - Philippines
  • PL - Poland
  • PR - Puerto Rico
  • PT - Portugal
  • RU - Russia
  • SA - Saudi Arabia
  • SE - Sweden
  • SG - Singapore
  • TR - Turkey
  • TW - Taiwan
  • US - United States
      Every state in the US!




(Click here)

The Curta Calculator Patent Poster was created by Aaron from MuseumOfLyrics.

This poster displays various detailed patent and engineering drawings of the Curta Calculator.

The poster has been created for A1 printing and is highly detailed, however it would look fine as A2. A3 would be fine but the drawings would look small.

This is a Digital File only and is for sale on the Etsy web site. https://www.etsy.com/listing/711993137/curta-calculator-patent-poster


The CURTA Collectors and Registry Page is a list of people who collect/own/like CURTAs!




Curt Herzstark

POB: Vienna, Austria
DOB: January 26, 1902
DOD: October 27, 1988
Parents: Samuel Jakob Herzstark [b.October 10, 1867 in Vienna d.October 24, 1937]
and Marie Herzstark [d.January 1956]
Grandfather: Benjamin Herzstark from Danzig [Poland]
Fathers Business: Austrian Calculating Machines Manufacturing Company, Vienna f.1905
Production was started at April 1, 1947.
In 1966 CONTINA AG was bought by the firm HILTI AG in Schaan.
Production was stopped on November 1970.
CURTAs were sold until early 1973.
There are +/- 80000 Curta I and +/- 60000 Curta II machines.
Curt Herzstark heard 150,000 to 160,000, maybe even more CURTAs were manufactured.

Type I

Type II

POB:Mauren, LiechtensteinMauren, Liechtenstein
DOB:April 1, 19471954
DOD:November 19701954
Sold Till:19731973
Capacity:8 x 6 x 1111 x 8 x 15
Parts:~600, 139 unique~719
Weight:8oz - 230g, 244g (measured)12 1/2oz - 360g, 372g (measured)
Diameter:2 1/16" / 2.08" - 53mm2 9/16" / 2.56" - 65mm
Height:3 3/8" / 3.35" - 85mm3 5/8" / 3.54" - 90mm
Height w/crank:4.21"/107mm4.38"/111mm
Case:4.73" x 2.40" - 120mm x 61mm5.13" x 2.88" - 130mm x 73mm
Total (Curt estimate):80,00070,000
Total (factory record):80,42761,660
Total (pictorial evidence):79,21861,061
Total (estimated):79,32069,942
Oldest (pic):000968500002
Oldest (registerd):2044500084
Newest (pic):80186561063
Newest (registered:80288569944
S# on top start:38210N/A
S# on top end:40469N/A
Black body end (pic):N/A510348
Black body end (registerd):N/A510395
Gray body Start (pic):N/A510536
Gray body Start (registerd):N/A510633
Metal can end:47753532716
Plastic can start:49815532511

Notes: type I
1- 7178 then a few more pin sliders were produced from 9321-9620.

Type I's with Serial Numbers on top row of bottom plate (most Curta's have the serial number on the bottom row of the bottom plate).
37840 (does not have SN on top)
oldest picture: 38600
newest: 40469
41416 (does not have SN on top)
It appears that at least a little over 1800 units (out of 80,000) have the serial number on the top row of the bottom plate.

Production in 1949 about 300 to 400 per month; in 1952 about 1000 per month
In 1949, only 300 CURTAs were made each month.
By 1952, 1,000 CURTAs were made each month.

Notes: type II
CUTRA 2s started at serial number 500,000.
The black type II case ended between 510348 and 510536.

The only way 540331 could be black would be if the bottom plate was switched or the calculator was assembled out of spare parts.


This page contain pictures of the oldest type I and type II Curtas. If you own a really old (or really new) Curta then send me your pics and I'll add them to this page if they qualify.


CURTA Production Date by Serial Number contains a discussion and two formulas to calculate approximately when your CURTA was made.

Here's a great article from Daniel F F Ford with a more precise method to determine the Curta's age: When was your Curta made?


Curta Manufacturing Evolutions

Curta Variations Curta Variations
Curta Variations Curta Variations

Above are three different styles of type 1 Curtas.
Notice the difference between the handle top, the entry knobs,
the labeling/lettering, and the storage cans?

Model Variations

serial # can crank body top decimal bottom decimal clearing ring entry levers
type I Curta 5 3
2185 metal metal black 5 3 metal pin
5790 metal metal black 5 3 metal pin
7278 (was 9897) metal metal black 5 3 metal rectangle
13836 metal metal black 5 3 metal rectangle
15045 metal metal black 5 3 metal rectangle
52335 metal plastic black 5 2 metal rectangle
58562 metal plastic black 5 2 metal rectangle
74738 plastic plastic black 5 2 plastic rectangle
type II Curta 6 3
504094 metal metal black 6 5 metal rectangle
526699 metal + leather plastic grey 6 3 metal rectangle
541431 plastic plastic grey 6 3 metal rectangle
557788 plastic plastic grey 6 3 plastic rectangle


Curt Herzstark - The Man

Young Curt-1910 Curt-1935s Curt-1942 Factory 1948 Factory 1950 Curt-1952 (from curta.li) Hobby Magazine 1954 Curt-1970? Curt-1970? Curt-1984 (from curta.de) Curt Herzstark chats with his former employee - Ing. Elmar Maier Curt-1985 Curt-1987 Curt 1988 Obituary Picture

Thanks to Prof. Karl Kleine from Jena, Germany, Curta.org and Curta.li for some of these pictures. If you have any other pictures of Curt send them to me. -Rick-


This is a wonderful document. A must have for all CURTA enthusiasts! -Rick-

Curt Herzstark, OH 140. Oral history interview by Erwin Tomash, 10 September 1987, Nendeln, Liechtenstein. Charles Babbage Institute, University of Minnesota, Minneapolis.

Herzstark, an Austrian inventor and manufacturer of calculators, describes the development of the Austrian Calculating Machine Manufacturing Company (Rechenmaschinefabrik der Austria Erstanden Compagnie) and his subsequent work in the industry. The company, founded in Vienna by his father, Samuel Herzstark, in 1905, introduced the first electrically-driven calculator based on improved designs of the Thomas Arithmometer. Herzstark describes the disruption of the industry during World War I, his involvement with the company after the war, competition with American companies, and his first invention, a mechanical memory for holding subtotals, which appeared in 1928. Herzstark managed the company in 1930 and began work on his own design for a hand-held calculator. With the Anschluss of 1938, the company was again converted to war production, and produced custom gauges for German tanks. Herzstark, a Jew, was able to avoid arrest until 1943, when he was sent to Buchenwald concentration camp and worked as a technician. He recounts his arrest and internment, and how he completed the design of the CURTA hand-held calculator, a prototype of which was produced in Weimar, Germany, by Rheinmetallwerke at the end of the war. The Prince of Liechtenstein bought the design and the calculator was initially manufactured by the CURTA division of Contina AG of Liechtenstein. It was produced until 1972, when the electronic calculator forced it from the market.

The transcript is available in English and German, and can also be downloaded from the CBI web site.


Backup Curta
(Click here)

Curt Herzstark and his Pocket Calculator CURTA.

A good article from backup magazine 6/88 page 5-9 and 1/89 page 41-45 This artice was translated by Andries de Man -- Thanks Andries!


A really good CURTA article from Product Engineering magazine -- October 1952.


This issue of the Report is based on an exhibit that allows you to journey through the history of the pocket calculator. You will meet the people who have used pocket calculators in the past and discover the problems they solved. At the exhibit you can try your hand at using their calculators. While in this publication, you will leam more of the anecdotes associated with the artifacts. Gwen Bell
(published by Computer Museum History Center, Winter 1987)


The Curious History of the First Pocket Calcualtor by Cliff Stoll. It was called the Curta, and it proved lifesaving when its inventor was trapped in a Nazi concentration camp.
(published by Scientific American, Jan 2004)

Also see Cliff's article from Reader's Digest: "Crunching Numbers - Jul 2005"


1/16/2021 - The newest version runs using WebGL (No 3rd party viewer required)!

A complete "Mechanical" Curta simulation. Watch every major part of the Curta turn and interface with it's mating piece.

Now you can see the step drum perform it's 10s complement magic, the gears turn, the transmission shafts rotate, the carry levers shift, and the digits count.

Spin it, flip it, zoom in, zoom out, explode it. Turn the crank slow, turn the crank fast.

Watch it operate in any position or view angle!

What would Curt Herzstark have thought! Amazing!

This is the new granddaddy of the Curta Simulators and must be tried!


Visit Olaf Veenstra's web page: YACS - Yet Another Curta Simulator


Curta CAD
(Click here)

Sebastian Dammers' 3D Curta CAD Model

Curta CAD Curta CAD Curta CAD

Check out Sebastian Dammers' 3D Curta CAD Model at GrabCAD.

Follow the arrows to get to the CAD model.

There's some discussion of the model at Curta.org.



Curta CAD
(Click here)

Onshape 3D Curta CAD Model

Here is a really nice model of a type I by mwu. It's 1:1 scale at nominal dimensions.  

This was use as the base design for the 3D Printed Curta.

Curta CAD
(Click here)

The 3D Printed Curta


Curta WiKi
(Click here)

Curta Wiki

This site includes every part in the Curta type I. The original engineering diagrams included on most of these pages are from the Museum Mura. A .zip file of these drawing can be found on this page: Curta Drawings


The CURTA Manual is a transcription of the CURTA Manual titled "Your CURTA Calculator" on one side and "The 4 arithmetical rules" on the other.

Here's a real nice version of the original 'Your CURTA Calculator' guide from The Curta Mania site:


Here's another .pdf version by Daniel F F Ford: Your-CURTA-Calculator.pdf


Curta Timing and Dimensions

(Click here)-Curta Timing (Click here)-Curta Subtract

(Click here)-Curta Dim 2 (Click here)-Curta Dim 3


Original Curta Service Manuals

NEW! Curta Service Manual in English

BIG Thanks to Hansjoerg Nipp!

type I in English

NEW! 8/22/21

type II in English

(Click here)-Curta I Service Manual
(Click here)
(59 pages - 31M download)

type II in English-Green

NEW! 5/12/22

type II in German-Green

NEW! 5/12/22

(Click here)-Curta I Service Manual
(Click here)
(43 pages - 46M download)
(Click here)-Curta II Service Manual-Green
(Click here)
(43 pages - 46M download)

type I in German

type II in German

(Click here)-Curta I Service Manual
(Click here)
(58 pages - 9.4M download)
(Click here)-Curta II Service Manual
(Click here)
(55 pages - 9.3M download)


These manuals are from the wonderful Museum Mura. Special thanks to Hansjoerg Nipp for all his contributions! Also see the assembly video (in my Video section below).


Original Curta Factory Drawings and BOM

Bill Of Materials

Curta type I BOM

Curta type II BOM

(Click here)-Curta I BOM
(Click here)
(14 pages - 3.5M download)
(Click here)-Curta II BOM
(Click here)
(14 pages - 4.3M download)

Curta Engineering Drawings (Blue Prints)

type I Drawings - 1950

NEW! 8/22/21

(Click here)-Curta Drawings
(Click here)
(257 .jpg files - 115M download)

Also available in .pdf format:
(257 pages - 115M download)

type I Drawings - 1960 B/W

type II Drawings - 1960 B/W

(Click here)-Curta Drawings
(Click here)
(217 .pdf files - 60M download)
(Click here)-Curta Drawings
(Click here)
(154 .pdf files - 28M download)

type I Drawings - 1960 Color

NEW! 8/22/21

type II Drawings - 1960 Color

NEW! 8/22/21

(Click here)-Curta Drawings
(Click here)
(208 .jpg files - 56M download)

Also available in .pdf format:
208 pages - 56M download)
(Click here)-Curta Drawings
(Click here)
(154 .jpg files - 39M download)

Also available in .pdf format:
154 pages - 39M download)


These files are from the wonderful Museum Mura. Special thanks to Hansjoerg Nipp for all his contributions! Also see the assembly video (in my Video section below).



CURTA Cleaning and Lubrication

I get asked all the time about how to clean and lubricate the Curta.
Click on the Lubrication image for some helpful email snipets from Nicholas Bodley and Jack Christensen plus some scans from the Curta Service Manuals.


Well I finally did it. Thanks to the support of my friend Carl Volkmar, I fully disassembled a type 1 Curta. The really good news is I put it back together and it still works! This page is BIG so go here only if you have a high speed connection or the time to spare. Each picture can be clicked on for a larger view too. -Rick-


Ever wonder how to work on a Curta? To do it right your need many specialized tools. Here are some of them from the collection of Hans-Rudolf Roshard.


I have discovered a total of 60 CURTA patents!

Curt was also assigned at least 19 patents related to various manufacturing processes and devices (sorry, I don't heve these published).

And 12 patents by Kurt Herzstark's principal engineer Mr. Elmar Maier.

I also have found 37 patents assigned to Curt's father [Samuel Jakob Herzstark] dealing with adaptations, additions and improvements to the Thomas calculator (sorry, I don't heve these published either).


Many thanks to Robert Häni for sending me these great pictures of his rare type 1A. And for writing the history of the 1A development. Enjoy...


Thank you to Hansjoerg Nipp for sending me most of these pictures.

Details of these early prototypes can be seen in some of Curt's patents.

Also notice the rare type 1A prototype (notice the serial number... 100049).



The Helmut G. Ayen Collection Page is a set of 33 beautiful pictures that I was sent from Helmut Ayen in Hossingen, Germany. He not only owns a pair of type I and type II Curtas but also a pair of type I and type II Demo Curtas! Enjoy the pictures and as always, click on any picture to get a larger version.


The Carlos Alberto Pedrosa Collection Page is a set of 18 beautiful pictures that I was sent from Carlos in Ribeirao Preto, Brazil. He own a very old type I (3920) and one of the first type IIs (5000008). Enjoy the pictures and as always, click on any picture to get a larger version.


Here is a great picture created by John Cherry. He was learning to use ray tracing software (POV-Ray 3.02). This is a picture of his Curta Type II (number 546692).

The picture uses 16 Million colors.

There are equivalent versions of POV-Ray for MS-DOS, Windows 95/98 & x86 NT, Macintosh, PowerPC, Amiga, SunOS, Linux (on Intel platforms) and generic Unix.

Great Job John!


Here is a large selection of special Curtas. Many of the pictures are from the collection of Hans-Rudolf Roshard.

The Skeleton Curta belongs to Richard Moor. He worked for Victor Comptometer, in Chicago, in the Research Center, as Prototype Model Maker from 1967-1976.

There are 3 cut-out "windows" on the clearing plate, 3 long "windows" on the upper knurled ring, 4 long "windows" on the lower knurled ring, 6 "windows" on the bottom plate, and the middle portion of the unit is open. All of the Lettering, Numbers and Arrows have been left INTACT, and the Little "rechnende Mocca-Mühle" is still fully functional.

The picture of a chrome Curta is from Stephan Weiss.

According to Reinhold Rehbein, the history says that, a short time before the factory in Lichtenstein was closed, Curtas were made from different spare parts. Almost every old Curta factory machinist has made a variant.


The CURTA company produced demo units for their sales force. According to a conversation with a factory trained repair technician, they only produced one demo unit per country that the Curta was sold in. If you own a Demo unit, send me a picture and I'll register it on the Curta Demo page.

Fake Curta Fake Curta

(Click here)

The Fake Demo Page

These are Curta's that are known to have been modified (cut) into demo versions.


Curta Pins

Curta Pins

These pins were made for an annual collectors meeting in Liechtenstein.

Thanks to Skip Godfrey for sending these pins to me.

I'd be real interested to learn if there were any other pins made and if there were more pins I'd like to get a picture to put on the web site. I'd like to know more about the annual meeting... email me with info... Rick Furr (rfurr@vcalc.net)

Curta Pins Curta Pins
photo from Jay K. Jeffries


This page contains pictures of Curtas that are on display in museums around the world. If you find any new museums/pictures send them to me and I'll add them to this page.


CURTA Literature Listing is a list of all know CURTA literature compiled by Rick Furr and Skip Godfrey. Please send us copies of your literature if it is different so we can include it.


The CURTA Articles page is where you will find interesting articles written about the CURTA.


The CURTA E-Mails page is a set of interesting E-mails that were distributed by Erez Kaplan's Calculating Machines List server.


These CURTA Ads were from Scientific American, June 1961 and June 1971 respectively.


Notice: Apr 04, 2017 - I talked with Jack and he's over a year behind in repairing CURTAs.
I don't recommend you send him your Curtas until further notice. -Rick-

Here are a few questions I asked Jack:

What do you charge to clean a Curta?

Typically $115 to $280, depending on the type of Curta [Type I or Type II] and the work involved. In those situations where only the upper carriage or the main body needs work, the fee will be at the lower end of the price range. More often than not, the entire machine needs a complete disassembly. It is my preference to thoroughly clean everything, so the charges are usually toward the upper end of the price range. If a full restoration is needed, the cost may even be higher. If something internal is bent, out of adjustment, or broken, the entire machine usually needs a complete disassembly.

What do you charge when repairing a Curta?

I charge $65 per hour of my time. It seems my hours are about 90 minutes long, however, because I rarely finish in the time I originally quoted. Extended repair time is absorbed by me.

What spare parts do you have? Are they expensive?

I actually have many hundreds of new original Curta parts. Most are for inside the instrument, though. I use them when I do general cleaning and repairs. Outer body pieces, replacement cannisters, and external parts that are easily damaged or broken due to abuse are not generally available, although I do occasionally locate some these items. Sometimes I have to fabricate a part, or repair an item as best I can. Obviously, this takes time, and the cost is high.

Parts costs are charged as the traffic will bear. I usually try to be blunt about this to the Curta owner, often telling them that a severely damaged unit is best sold as a "parts Curta". Unfortunately, I've sometimes had to tell this to someone who wanted to repair a Curta looked upon as an heirloom. What to them appears to be a minor issue actually turns out to be a major problem (e.g., a crank handle tilted downward is due to a broken main shaft).

Costs for both a cleaning and typical repair is often between $150 and $250. I think the most I ever charged for a repair was about $500...there were many serious problems with the machine. Generally, when the price gets to be above $300 many people simply keep the damaged Curta as a memento.

Can you replace a clearing ring? What costs are involved?

Plastic clearing rings are available. I have several new ones, but I typically do not sell them separately as a spare part. Rather, I install them during a general cleaning and repair. I can modify a Curta that originally had a metal clearing ring to allow a plastic clearing ring to be used. There are special rivets for this purpose, which I have.

Metal rings are more difficult to replace. As with the plastic clearing rings, I will only install a metal clearing ring during a general cleaning and repair. It takes a special tool to properly swage the rivet in place. [Editor's note: Very old Type I clearing rings were held on with a screw and nut. The nut was crimped to the screw threads below the clearing plate. Don't turn the screw! You'll break the screw and/or strip its threads!] I have only a very few new metal clearing rings for both the Type I and the Type II. I also have used metal clearing rings [that were removed from damaged Curtas] for both the Type I and the Type II. The new Type I metal clearing levers are so rare that I will only install the ones I have on very old or very special machines. The cost for a new Type I clearing ring is extremely high. The rivets needed to install a clearing ring are special too, but I do have a few.

Jack's company, Timewise also manufactures a line of rally equipment for TSD competition. The units include TSD computers for running in a Computer Class, units designed for Odo Class competition, and competition and checkpoint clocks. Jack can be contacted for special-order equipment or particular modifications desired for Timewise equipment. Jack also repairs older Zeron equipment. A wide selection of sending units are available.

Jack Christensen
32 Old barn Road
Hawthorn Woods, Illinois 60047
(847) 550-5052 (evenings)


Hans logo
Click here to visit: https://www.curta-schweiz.ch/

Repairs, Revisions, Cleaning, and Accessories

Curta Switzerland service center and Watchmaker's workshop & precision engineering workshop

I have been fascinated by watches since my earliest childhood. After studying at the University of Applied Sciences in Furtwangen/Germany, I worked in the watch industry for over 20 years. As a watch engineer, I was able to develop many well-known wristwatch models. My employers included IWC (International Watch. Co.) Glashütte Original, Lange & Söhne, Vulcain and Antoine Martin.

In 2015 I became self-employed and realized that there was a great need for the revision of large clocks. In addition to approx. 30 large mechanical clocks (Comtoise, pendulum clocks, grandfather clocks) , I also service pocket watches, wristwatches, music boxes and mechanical devices of all kinds every month take over Switzerland.

I am passionate about repairing mechanical movements of all kinds. Over the years I have acquired a machine park in the basement of our house, with which I can produce spare parts myself.

I was able to realize my childhood dreams: today I run a watch workshop in Switzerland, in which we offer revisions and repairs over 1,000 small and large watches as well as Curtas at very fair prices. Our workshop is located at Zurich Airport, only a 10-minute drive from Bülach. Visitors from all over the world are always welcome!

Service Curta Switzerland
Matthew Schneider
Alte Winterthurerstr. 5
CH-8180 Bülach/Switzerland
+41 44 860 00 45
E-Mail info(at)repair-workshop.ch


If your Curta is damaged or if it doesn't work correctly, if it needs revising or just cleaning and you want it back working and in perfect shape, this is the right website for you.

We repair, calibrate, tune, revise and clean these mechanical wonders. We have been doing this for years for a limited group of collectors, but now we have decided to start operating on an international level.

You can send us your Curta and, completely free of charge, we will let you have our estimate of the costs of our service. As an alternative, we will assess the value of your Curta (whatever its condition) as a firm offer to buy it from you.

If you are not willing to accept our proposals, we will send your Curta back to you, without any further cost on your part.

As you have certainly noticed from our simple and essential website, we do not intend to impress anybody with special effects: we just work hard and seriously, and we guarantee the results of our work.

If you need any further information or if you have any doubt or question to ask, do not hesitate to contact us: info@curtaservice.it

Romano Manaresi - Ravenna, Italy, September 2010



Curta, Carena & Co. - Book Information


In the early 1930s, Curt Herzstark was thinking about a small mechanical pocket calculator in the big city of Vienna. At the same time, agricultural life and small trade still prevailed in Mauren, Liechtenstein.

Soon after the end of the Second World War, the Princely Family of Liechtenstein, which was looking for new businesses to settle in Liechtenstein, heard about the little calculating marvel and contacted the inventor Curt Herzstark. He was able to further develop his little calculating machine during his time as a prisoner in the Buchenwald concentration camp. After his liberation from the concentration camp and an adventurous escape to Vienna, Herzstark tried to find backers for his "Liliput" calculating machine. Talks with the Princely Family in 1946 led to the founding of the calculating machine factory Contina AG and the construction of a production plant for office and calculating machines in Mauren. The calculating machine, soon called "Curta", became the only mechanical pocket calculator ever produced in large quantities in the world. It was used primarily by merchants, technicians, architects, engineers, chemists and scientists.

Herzstark withdrew from the company after successfully setting up the production of the calculating machines and after some turbulent developments in the financing of Contina AG. Contina soon diversified into various products such as measuring equipment, reflex cameras, record players and film cameras. However, many of the developments had to be discontinued because of technical problems or because of misjudgements of the market.

In the mid-1950s, the boom in amateur film began with the 8mm cameras. Contina invested large sums of money in the development of film cameras. These were distinguished by a spring drive specially integrated into the handle and an elegant design. They received a lot of attention from experts, but in the end they were not able to prevail against the overpowering competition, which was also always one step ahead. In 1965, the company was financially finished and was taken over by the construction technology company Hilti AG. Hilti AG was in a major expansion phase at the time and was thus interested in the qualified employees and the buildings with the infrastructure. With the exception of the Curta calculating machine, which was built until 1971, the production of all Contina AG products was discontinued. The Curta is still highly sought after by collectors of historical calculating machines.

In the years following the takeover, the Hilti factory buildings were greatly expanded. The jobs in Mauren remained, albeit with completely different work content, until 2010. In 2013, the buildings were demolished and turned back into a greenfield site by 2015.

Contina AG was the first industrial company in Mauren and thus very important for the community's entry into the industrial age. The company created many jobs and apprenticeships and played a decisive role in Liechtenstein's transition from an agricultural country to an industrial country.

The book is available:
   o In German bookstores.
   o At http://www.buchzentrum.li/Webwinkel-Product-212847644/Curta-Carena-&-Co.html for CHF 48.00 plus shipping.
   o From the author ( curta(at)dsl.li ) at the reduced price of Euro 34 plus shipping costs.

The author

Hansjörg Nipp, born in 1951, retired engineer. During his active professional life he worked first in research and later as a project manager in a large Liechtenstein industrial company. For many years he has been concerned with the history of the Contina company and its products such as the famous Curta calculating machine. In 2007 he curated a highly acclaimed special exhibition at the MuseumMura about Contina and in 2009/2010 he worked as a technical advisor on the filming of the inventor portrait "Herzstark" by Kuno Bont.

Curt Herzstark Book (in German)


Curt Herzstark's memoirs were written down by his partner Christine Holub after many conversations recorded on audio cassettes. Christine Holub was supported by her friends Ute Schröder, Bernd Schröder and Heinz Joss in editing this transcript with a view to publishing it as a book.

The title "Kein Geschenk für den Führer - Schicksal eines begnadeten Erfinders" translates to "No Gift for the Leader - Destiny of a gifted inventor"

Curt Herzstark Book (in English)


This Oughtred Society’s translation of the autobiography of Curt Herzstark, the inventor of the CURTA calculator, is a must have for a CURTA collector or enthusiast. This book documents the life of Curt Herzstark, his youth in Vienna, his education and travels with his father (also an inventor of a calculating machine), his internment at the Buchenwald concentration camp, and his post-war difficulties in the production and distribution of the CURTA calculator. Additionally, appendices provided by Tom Wyman and Bob Otnes provide additional information about the use and derivation of the CURTA calculator. Many photographs are included.

English, Perfect Bound, 8½" x 11", 180 pages, 20 ounces,
$36.95 plus shipping.
Order at www.oughtred.org

Pattern Recognition Book


The Curta is featured in the novel Pattern Recognition by William Gibson, where the heroine trades one of the first ever produced Curta for a valuable piece of information from a former spy who is now a collector of mechanical calculators.

Curta-Handbook-s-l400-1 Curta-Handbook-s-l400-2 Curta-Handbook-s-l400-3

CURTA Calculator: The Handbook

A New Concept for Using the CURTA Calculator

by Bernard Stabile ( ber.stabile(at)free.fr )

It is a true "modern tribute to the genius of CURTA"

With its visual algorithms in the form of tables, the calculation sequences become attractive, and of an exceptional aesthetic presentation. The pleasure of using the CURTA is multiplied. It includes the amazing possibility of CURTA to quickly calculate the area of any polygon. It also includes some new algorithms such as a succession of magic numbers as well as the golden number or the date of birth of any CURTA calculated by the machine itself !

21 remastered algorithms:

o Addition - Subtraction
o Multiplication - Division
o Division by breaking down
o Continued multiplication
o Rule of three
o Simultaneous calculations
o Square root
o Power calculation
o Pytagoras’ theorem
o Area of a polygon 1
o Area of a polygon 2
o Magic numbers
o The phoenix
o Lewis Carroll's number
o The golden ratio
o Date of birth of a CURTA

High quality of realization. An essential collector for any CURTA enthusiast.


Postage Stamps

CurtaStamp-tn CurtaStamps-tn

"Technical innovations in Liechtenstein"
The stamps were released in 2006 by The Liechtenstein Postal Service
The series' technical innovations from Liechtenstein presents "inventions that were developed in Liechtenstein and conquered the world market. In the first two series, the Curta calculator, the camera Carena, the caliper of the PAV and the Hilti Hammer, Kaiser walking mobile excavators and the heating surface aluFer were presented by the Hoval.



Design For The Real World by Chris Spurgeon - Audio

This is an audio track by Chris Spurgeon about the Curta. It was broadcast by Studio360. The show is called "Design For The Real World".


Cool YouTube Videos

Curta Assembly Video


Published on Nov 22, 2013
Zusammenbau einer Curta Rechenmaschine
Demonstration of CURTA calculator assembly
CURTA was manufactured from 1949 to 1971 at Contina AG in Mauren, Liechtenstein
CURTA history is displayed in the museum MuseumMura, 9493 Mauren, Liechtenstein
Website www.museummura.li

Tech Icons: Cliff Stoll - The Curta Calculator

The legendary Cliff Stoll tells the story of the invention of the Curta Calculator

A Visual Guide to Mechanical Computing presents The Curta by Mike Hilton

This is a great instructional video based on Olaf Veenstra's YACS VRML Simulator!

The CURTA was featured on The History Channel's Pawn Stars on May 2nd, 2011

The PawnStar's CURTA segment.

Watch the segment: HERE

The Assembly of YACS - Yet Another Curta Simulator by olafzijnbuis

YACS - Yet Another Curta Simulator. A Guided Tour by olafzijnbuis

The Astounding Curta Mechanical Calculator by rregister

Curta mechanical calculator by Gyroscopes

Square root of 2 using the odd subtraction method by HifiCentret
Now go try Newtons method [ A=((N/A)+A)/2 ]...


Links to other CURTA Calculator pages:

* "The world's first, last, and ONLY, mechanical handheld pocket calculator." credit to Jim Chen, Fair Lawn, NJ!

The Calculator Reference by Rick Furr (rfurr@vcalc.net)
Back to The Calculator Reference