The Curta Calculator

You could be forgiven for thinking that being called a “Curta-cranker” was a bit of an insult. The nickname describes someone who constantly cranks their Curta (!) to make calculations. However, the Curta calculator, as the hallowed invention of concentration camp survivor Curt Herzstark, has become such a collector’s item these days, that just to have one in your possession is a fact worth celebrating. It means you are one fortunate, and determined, collector.

In a sense, I am a that determined collector. I have been trawling the flea markets for more than 2 decades in the quest for bargains. I collect almost everything that I believe is cool, of historical interest and which catches my attention. But with one important precondition: I am a collector of quality. And the Curta is a magnificent example of the kind of object that collectors like me regard as the Holy Grail of the antiques world.In many ways, the Curta perfectly complements any impressive tool watch collection.

In the past, watch brands like Omega, Universal and Heuer advertised their watches showing Curta calculators in their marketing campaigns, so the Curta has become part of the family in the minds of many watch collectors. Curtas particularly match 1960s racing watches, as the ingenious calculators were used as accurate measuring tools in rally races. In fact, the Curta has always been associated not only with sports and watches, but also with aviation and engineering, as the canny calculators also match pilot watches like the Navitimer. The Curta is not only one of the coolest pieces to add to any man’s toy collection, it is also a great conversation piece because of its rich history, which I will explore a little now.

Herzstark was born in 1902 and grew up in Vienna, where his Jewish father had established a factory manufacturing calculators and other precision instruments, so naturally the young Curt followed in his father’s footsteps. As a salesman for the firm, Curt soon realised there was a huge demand for a new kind of portable calculator to replace the bulky, heavy and expensive models of the time. But any dreams Curt had of designing such an instrument himself were scuppered when war broke out in 1939 and the Herzstark factory was ordered to make tools for use in the war effort.

Because of his Jewish connections, Herzstark’s career became very precarious in Nazi Germany and by 1943 he found himself an inmate of Buchenwald. Luckily, his talents as an instrument maker were recognised and he was allowed some free time to work on his plans for a new, smaller calculator that would fit in the hand of its owner. As Herzstark explained much later in an interview: "The head of the department, Mr. Munich said, 'See, Herzstark, I understand you've been working on a new thing, a small calculating machine. Do you know, I can give you a tip. We will allow you to make and draw everything. If it is really worth something, then we will give it to the Führer as a present after we win the war. Then, surely, you will be made an Aryan.' For me, that was the first time I thought to myself, my God, if you do this, you can extend your life. And then and there I started to draw the Curta the way I had imagined it." By the time Herzstark and the other survivors saw the death camp liberated in 1945, his prototype drawings were almost complete.

Following his new-found freedom, Herzstark experienced another stroke of luck when his talents were also recognised by none other than Prince Franz Josef II of the Principality of Liechtenstein, who invited the Curta man to work on his calculators in a new, specially built factory in his tiny country. A new company was formed, Contina AG, with Herzstark as technical director. It took a few more years for the Curta to finally appear in 1949, with a price tag – high at the time – of $125. The new calculator was handy, efficient and ingenious, a pepper-pot-sized drum design more accurate than a slide rule and more user-friendly than anything imaginable at the time.

So how does the Curta work, exactly? Well, if you imagine a pepper-pot shaped metal barrel with a winding handle at the top and a ring pull next to it, that is the basic design. The handle, or crank, is turned clockwise to make the calculations. Around the barrel are a set of tiny levers or slides which can be lifted up and down to create the numbers you wish to calculate. At the top, you find two sets of corresponding numbers: the black numbers on a white background show the number of times the handle has been turned to make the calculations, and the white numbers on a black background show the result of the calculation. And all this in the palm of your hand, weighing only 230 grams (8 ounces).

Perhaps Herzstark’s most inspired engineering trick was the inclusion of two sets of teeth within the barrel: one for addition and multiplication and another for subtraction. Herzstark hit on the idea of using the complement system (complements are the constituent numbers which add up to 9, so the complement of 8 is 1, while the complement of 5 is 4, and so on), which basically means adding numbers to work out a subtraction. Instead of turning the crank anti-clockwise to subtract, the handle can be lifted up slightly until a little red band appears, and then turned clockwise to engage the upper set of teeth and hey presto! – you have made a subtraction. Pure genius. 

Only two models of the Curta were produced during its 23-year reign. The Type I Curta has eight sliders, a six-digit revolution counter, and an eleven-digit result counter. The larger Type II Curta, which appeared in 1954, has eleven sliders, an eight-digit revolution counter, and a fifteen-digit result counter. The type II is heavier than the Type I, weighing in at around 370 grams (13 ounces). Around 140,000 Curta calculators were made in total (80,000 Type I and 60,000 Type II) between 1949 and 1972.

The popularity of the Curta among rally drivers was due to two salient facts: Herzstark’s invention was irrefutably accurate and, at the same time, tough enough to take the knocks of high-speed racing. So much so, that rally teams continued using their Curtas to measure times, speeds and distances into the 1980s, despite the emergence of modern pocket calculators. Racing drivers who swore by their cylindrical devices earned the memorable nickname of "Curta-crankers".

The precision of the Curta also attracted pilots, who needed highly accurate results when checking such things as weight, balance and other calculations essential in determining the safety of their aeroplanes. Being virtually error-free, the Curta’s mechanical rigour can always be relied upon to calculate precisely, especially when you are facing a life or death situation. 

So, basically, that’s the story of the Curta. For me, with its rich and remarkable history, the Curta is much more than just another cool piece to own and a nice conversation piece: I think today it’s a kind of big brother to the more famous Rubik´s cube. A big brother who is older, wiser and much more stylish.

As a dedicated watch collector who religiously hunts through the flea markets every weekend, it was inevitable that I would develop a personal, collector’s relationship with this elusive and fabulous engineering piece. I bought my own Curta calculator not only because it’s a fantastic instrument with a great history, but also because I could not resist the deal I managed to broker at the time. Even though I paid more than US$300 for mine, I realise now what a scoop that was, as sometimes they can fetch up to $2,000. You see, collecting is not just about finding the gems buried under all that worthless rubble: it is about finding those gems that are enticingly undervalued by the seller. It’s about the snip, the steal, the give-away.

These days, the Curta calculator has easily achieved the status of a high-end commodity in the collectors’ world, on a par with Leica's, Tiffany's or Faberge. Personally, I don't specifically collect these kinds of objects because of their brand or their high price, but because I appreciate quality and I know a gem when I see it; and when I find something with a good price and in excellent condition, I can’t resist. So, after 30 years of collecting I now own 2 Curtas, the Leica's M2 and M3, a Tiffany's lamp and some Faberge pieces. Even so, I still don't consider myself a collector of these objects; I just own some because I was lucky enough to find them, at an irresistible price, during one of my many, determined quests.

So, to all you Curta owners out there, why not share your own experiences of tracking down this beautiful design piece, and tell us just what Curt Herstark’s unique invention means to you?

Happy hunting!
Dan Henry

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