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Curta – a collector’s gem

26. July 2019 | Technology

The smallest mechanical calculator in the world was a sensation at the end of the 1940s – and so it remains today. It is regarded as the legacy of original inventor Curt Herzstark from Vienna, who spent his time at the Buchenwald concentration camp producing design drawings as what was referred to as an “intelligence slave”.

The mechanics of the Curta are said to be comparable with those of a watch movement. In the 1950s, the handy and stylish Curta had advanced to the role of trusty companion to architects, surveyors, engineers and craftsmen. It ran like clockwork: the 571 individual parts in the first model, the Curta 1, were orchestrated in such a way that the elegant device could be used to perform the four basic arithmetic functions and later, in the second version, even root extraction with the utmost precision. But the whole is greater than the sum of its individual parts. How did Curt Herzstark, son of a calculator manufacturer, succeed in creating a mobile pocket calculator after so many other expert contemporaries had failed?

Curta – an old invention rediscovered


Herzstark quickly discovered that the existing calculators could not be made much smaller. So instead, he used the dimensions and the precision mechanics of a watch movement, a pocket watch, as a guide and considered how he could enlarge the tiny mechanism. He approached the problem from a different angle. He acted as if he had already invented the pocket calculator and had had the special shape of the device firmly anchored in his mind beforehand. In doing so, he took customer requirements into consideration too – keeping his finger on the pulse of the market. His technical skills, his unconventional way of thinking and practical experience from his work at his father’s factory came together to enable him to house the complex mechanism in the round case with the crank handle.

Design of the Curta

Curta forever


Following liberation from the concentration camp, Curt Herzstark later heeded the call of Prince Franz Joseph II, who laid the groundwork for the production of the pocket calculator in the municipality of Mauren in Liechtenstein. Today, the Contina-Weg path evokes the memory of the one-time production site – which closed its doors for the last time in 1971. The Curta is so much more than a fantastic product that was surpassed by electronics. It saved its inventor’s life in a concentration camp. If you look into how it was created, you will come across its creator, a creative, highly motivated person with extraordinary inner strength, technical skill and artistic talent. In spite of resistance and adversaries, in 1948, Herzstark and his team launched the first and smallest mechanical pocket calculator on the market. Today, the Curta is not just an intelligent toy for maths enthusiasts and a collector’s gem, it is also proof that determination and belief in your own abilities can overcome (almost) all obstacles. Thank you, Curt Herzstark.

Demonstration of the four basic arithmetic functions of the Curta II

Related to the watch?


Retired repair expert Hans-Rudolf Roshard from Zurich, who has repaired roughly 700 Curtas from all over the world in his lifetime, limits the similarities between a Curta and a watch to the sophisticated precision mechanics. “The Curta operates with a stepped roll; this technology is not present in watches.” Walter Beck, the recently deceased founder of the Calculator and Typewriter Museum in Schaan, Liechtenstein, goes a bit further. One of the comparisons chosen by him was with the historical calculating machine created by German pastor Philipp Matthäus Hahn in 1770. Hahn was an esteemed watchmaker; when inventing his calculator, he used a stepped roll and favoured a kind of box form.


Beck saw another historical connection to watches in the time-honoured pocket-size Swiss calculating clocks. Here, the parallels with the world of watchmaking are clear. This is also confirmed by Hansjörg Nipp from Mauren, Liechtenstein, who is currently writing a book on this topic. He points out that, initially, it was largely experienced watchmakers and precision mechanics from neighbouring countries that were hired for the production of the device at Contina AG. From that, he concludes that people who can handle the delicate mechanisms of watches with skill have the necessary expertise and often an interest in creating outstanding mechanical pocket calculators.

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