My wife gifted me a CURTA Type I mechanical pocket calculator for Xmas. Thank you, Love! This model (SN 58858) was manufactured in January 1965 by Contina AG Mauren, Liechtenstein. The CURTA calculators – two models exists – were produced between1948 and 1972. They both can add, subtract, multiply and divide, with more or less precision.

This mechanical marvel is Curt Herzstark‘s brainchild, the son of a Jewish father and Austrian mother (1902 – 1988). He demonstrated his early engineering and management talent in his father’s company, Rechenmaschinenwerk Austria Herzstark & Co., where father and son sold and improved mechanical calculators. If you wonder, in the early 20th century, there was nothing other than mechanical calculators and different abacus, tables, or slide rulers.

Although half-Jewish, Curt could continue operating the family company as an army supplier during the second world war. However, in 1943 he was arrested and deported as a slave worker under SS supervision in the Gustloff Werke-Weimar factory (Buchenwald concentration camp). It is said that he was allowed during his free time to work on his project – the CURTA – so his pocket calculator could be offered to the führer for the victory. Luckily that didn’t happen, and the war was won by the allies in 1945.

At the end of the war, in 1947, after building a few CURTA prototypes, Curt was on the market for investors so that he could mass produce his invention. Although the CURTA was revolutionary then, he could not find any. In fine, it is Franz Joseph II, the Prince of Lichtenstein, who offered to fund the production of the calculator, which explains the unusual Made in Liechtenstein. You can even buy today a CURTA box and the user manuals from the State Museum shop (here). Since we are on the topic, as you may guess, there are few places where you can service your CURTA. And for sure, I would not attempt the operation myself. Fortunately, in the US, Timewise, an electronic design, and manufacturing company in Illinois specializing in automotive rally equipment since 1976, offers CURTA repair and servicing (here).

Timewise explains its involvement in the CURTA servicing: “Also in 1986, Timewise started a cleaning and repair service for the semi-antique Curta mechanical calculator. The Curta calculator is often used in vintage car rallies. Because the Curta requires regular maintenance, Timewise undertook the responsibility of providing this essential service to vintage rally participants. By arrangements with retired Curta service personnel, Timewise acquired factory assembly tools and new replacement parts, and became the only recognized source for Curta repair in North America. The popularity of eBay has also significantly increased the interest in these mechanical marvels. As a result, the call for Curta repair service continues to grow.”

Surprisingly, the CURTA – both types – are exceptionally well documented. I wish other computing devices had similar coverage. Therefore, I will not try paraphrasing excellent content you can find online (and I will share several links hereafter). As a computer scientist, I will highlight the programming model of the CURTA, which can be found here. It is an original and remarkable way to describe the CURTA operations if you are used to reading up on CPU architectures, instructions sets, etc. Alas, as sophisticated as it is, there is nothing more one can do with a cheap electronic four-banger. But this would be to overlook the fantastic build quality of the calculator—something challenging to convey or imagine without handling and operating the device. Although mechanical computers are of excellent quality (here or here), the CURTA is at a level I never experienced. It is a unique tactile and sonic experience!

Before I end sharing with you the links I mentioned earlier, let me remark on Marcus Wu‘s 3D-printed CURTA project (here). If you are a skilled 3D printer/maker with some spare time, it can be a challenging project to tackle.

  • YACS, Yet Another Curta Simulator (here)
  • A CURTA site for francophones (here)
  • Print and build your own CURTA (here)
  • All you need to know on CURTAs (here)

This post is the first I have published in a while. Indeed, I went – and still do – through rough patches that made my publishing sparse. For 2023, I will resume regularly sharing my topics of interest. Stay tuned. In the meantime, I wish you and your beloved good health, happiness, and success in all your endeavors. Happy new year!