The Curta calculator, invented by Curt Herzstark while he was a prisoner at the Buchenwald concentration camp, is one of the most beautiful tools a mathematics enthusiast can aspire to. With a shape that resembles a pepper grinder, it uses a series of sliders to enter numbers and a crank to perform calculations. Today it has become an expensive collector's item, but for years it was considered one of the best calculators you could buy.
Sometimes, an artifact designed to serve as a simple tool becomes an object that—whether because of its appearance, history, or design—transcends the merely functional and becomes far more interesting. That is undoubtedly the case with the Curta mechanical calculator. This small device, designed by Curt Herzstark while he was a prisoner of the Germans at the Buchenwald concentration camp, was born as a calculator, but decades later it has become a true cult object.
The History of Curta Calculators
The story of these calculators begins when its inventor—who fortunately survived the terrible experience of living in one of those camps—was freed and was able to refine the mechanisms he had conceived during his captivity. In 1948, after the end of World War II, the company Contina AG Mauren, of Liechtenstein, began manufacturing the device designed by Herzstark.
It was quickly considered one of the best handheld calculators available on the market. It must be remembered that at that time a typical “normal” calculator was a device weighing several kilograms and about the size of a shoebox. The “Curtas,” as they were commonly called, were only surpassed with the appearance of electronic calculators and their popularization, around the 1970s.
From a physical standpoint, the Curtas were small, cylindrical, with a series of levers (commonly called “sliders”) on their sides and a small crank on top. Their size makes them suitable to operate anywhere, since they fit comfortably in the palm of the hand. The sliders are used to enter numbers, and the crank to perform operations. Depending on how the crank is turned, the Curta can add, subtract, multiply, divide, and—with some extra work—extract square roots.
On the top (the “lid”) there are two indicators called “revolution counter” and “result counter,” which show the number of revolutions made by the crank and the results obtained. You might be wondering how a single crank can perform different mathematical operations. The answer, of course, lies in the intelligent design of its internal mechanism, which allows the crank to add when turned one way, subtract when slightly pulled outward before turning, and perform other operations using similar tricks.
Despite its simple exterior—even “minimalist,” if you will—the Curta's internals are made up of more than 600 individual pieces. Curt Herzstark designed his calculator based on prior work by Gottfried Leibniz: the “arithmometer.” The values it operates on are stored on toothed wheels, and sums and other operations take place on a drum mechanism known as the Stepped Reckoner. As with the abacus, a Curta in skilled hands can produce results faster than an operator using an electronic calculator.
It is no accident that Herzstark invented this device. Before becoming a prisoner of the Nazi regime, he had inherited from his father the Rechenmaschinefabrik der Austria Erstanden Compagnie (Austrian Calculating Machine Manufacturing Company), a company that had gained some fame by building the first electric calculator in series. The same Curt was designing such artifacts, and in 1928 he had invented a mechanical memory system that stored partial numerical values in the calculators of the time. When, in 1943, due to his Jewish condition, he was sent to Buchenwald, the guards discovered his ability and decided to separate him from the heavy work he was doing so that he could build “a gift for Hitler.” The gift in question was nothing less than a prototype of this calculator, and his work on that project while imprisoned was what kept him alive.
After the conflict ended, Herzstark sold the perfected design of his device to the Prince of Liechtenstein, and a company from that country—Contina AG Mauren—began manufacturing it in series. The first model produced was the “Curta Model I,” which has eight sliders—that is, it can work with numbers up to eight digits—a six-digit revolution counter, and can display results up to eleven digits.
It is estimated that about 80,000 units of this model were produced during its production run. They cost the equivalent of about 600 dollars. In 1954, the factory began producing a slightly larger model, the “Curta Model II,” with eleven sliders, an eight-digit revolution counter, and results up to fifteen digits. About 60,000 of these calculators were sold before the factory ceased production in the face of new electronic models.
Over the years, Curtas were used by merchants, mathematicians, and scientists. But they had some unexpected uses. Race car drivers, for example, used them to perform calculations during competition, and many airplane pilots carried one to assist with navigation. The two models were very robust and reliable. Only 3% of buyers sent their calculators back to the factory for repairs.
Ironically, a large part of that percentage corresponds to users who disassembled their Curta and discovered with surprise that it was almost impossible to reassemble its 600 pieces. In those cases, Contina AG charged them a “reassembly fee” equal to half the value of a new Curta. Legend has it that the manufacturer sent them back to their owners with a note reading: “Do not feel bad. The Curta really costs 900 dollars, since everyone takes them apart.”
Anyway, this calculator, known—due to its shape—as the “pepper grinder,” has become a scarce cult object, and collectors often pay several hundred euros for one. Did you know about them?
