So some of you know what this is and why it is special. But many do not, and have asked. For those of you who are not familiar with it, or the history of how it came into being, it’s worth the tale.
https://twitter.com/Srasgon/status/1505005111180861449
This is a Curta calculator #curta
Today everyone takes calculators for granted. You have an app on your phone. Or you can buy one of meaningful complexity for a few dollars.
But people forget that this was not always the case. We sent people to the moon using slide rules after all.
People have wanted the ability to do computation for centuries. Things like the abacus have been around for thousands of years after all.
But mechanical calculators that could add, subtract, multiply, and divide have been around since maybe the mid 1600’s.
But they were typically huge things, decidedly not portable
For portability you needed something like a slide rule (which has its own charms and is useful, but not what people were really looking for in this context.
Enter Curt Herzstark, Austrian engineer.
Growing up Herzstark’s family built mechanical calculators (the big ones) in their factory in Austria.
And he grew up around them.
But in the 1930’s, in his 30’s, Herzstark starting thinking of some way to build a mechanical calculator that would fit in your pocket. By the late 30’s he was ready to start building it.
And then World War II happened.
In the beginning of the war Herzstark’s factory, at the request (demand) of the Germans, retooled to make war materials for the German army, so the small calculator would have to wait.
But in 1943 Herzstark (who was half Jewish) was himself taken away, and thrown into the Buchenwald concentration camp.
In the camp he (like many others) came close to death. But the Germans learned of the handheld calculator had been designing. They hence kept him alive, and allowed him to continue the design work on it.
So this calculator quite literally saved his life.
During his time there, amid the pain and death all around him, in the worst situation imaginable, he continued to work on his design.
In 1945 when Buchenwald was liberated Herzstark was released, with the now-completed drawings for his calculator on scraps of paper in his pockets.
He walked to Weimar, and had three prototypes made. And then made his way back to Austria, where (amid the rubble of the war) he filed patents on the device, and looked for investors to bring it to fruition.
He eventually found only one party interested.
The prince of Liechtenstein.
The prince of Liechtenstein.
Liechtenstein created a company, Contina Ltd, and began building Curta calculators. An initial run of 500 were built and went on sale in 1948.
The Curta calculator, in 2 versions (type 1 and type 2, which could handle larger numbers) sold steadily for 25 years, from 1948 to around 1972. The type 1 (with an 11-digit capacity) sold for $125; the type 2 (15 digits) for $165.
The Curta was used by engineers, surveyors, accountants etc. Interestingly, they were hugely popular with rally racers, who needed to calculate things like mileage & fuel usage while on the go, with the Curta’s fine engineering proving robust enough to handle the abuse of a race.
In the early 70’s cheap electronic calculators started to become available, which, disappointingly but understandably put an end to the Curta’s run.
Over 25 years about 150,000 were sold (~80,000 type 1, and ~60,000 type 2).
But for 25 years if you wanted something that could add, subtract, multiply, & divide, & could fit in your pocket, the Curta was virtually your only option.
And to this day the Curta type 1 remains the smallest (and most exquisitely engineered) 4 function mechanical calculator ever made.
They kept good records too, so given the serial number you can tell when a given Curta was made. For example, this one was manufactured in 1958. And it works almost as well now as it did out of the box, amazing for a precision device that is almost 65 years old.
This particularly one is a (fairly) early Type I. Later models began to use some plastic parts, but the earlier models (like this one) were all metal. 
Want to see how it works?
Here are the basics
Adding numbers is easy
Subtraction is fun too (it uses 9’a complement subtraction, so it’s actually doing addition to accomplish the subtraction)
We can multiply and divide as well. Here is a multiplication demo; division is a bit more complex (will save that for another time) but it can be done!
There are algorithms to do square roots, logarithms etc as well. It’s a surprisingly robust piece of kit.
And it’s viscerally satisfying to operate, in a way that punching numbers on an electronic calculator is not. Feeling the gears clicking over in your hand is actually quite the experience.
Unfortunately these are somewhat expensive. You’ll likely find examples ranging from ~$1500 to $2500+. This one cost me ~$1800.
I have been wanting one for years, since they were $500, and finally caved.
I have been wanting one for years, since they were $500, and finally caved.
Though inflation-adjusted the original $125 would be ~$1200 today. So they’re not all that far off!
And this one, almost 65 years old, works almost as well as it would have coming out of the box brand new. A remarkable example of some of the finest engineering of the 20th century.
Who cares if it’s obsolete?
I love it!
I love it!
If you are interested in how exactly the Curta works, this video is informative (and mind blowing)
BTW this story has been told by others much better than me. I particularly like Cliff Stoll’s narrative.
One more video - @donttrythis talking about the Curta, as well as unveiling a 3D-printed version made by @marcuswu (really great)
One more #curta tweet - I had promised to show you how to do division on it. It’s a little more involved but the Curta can do it, and give you the decimals to the limiting precision of the counting (white) register (the division answer gets read out there). Here’s how (part 1):
And part 2:
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