The Curta is a small, hand-cranked digital mechanical calculator introduced by Curt Herzstark in 1948. It can be used to perform addition, subtraction, multiplication, division, and (with more difficulty) square roots and other operations.
The Curta’s design is a descendant of Gottfried Leibniz‘s Stepped Reckoner and Thomas‘s Arithmometer, accumulating values on cogs, which are added or complemented by a stepped drum mechanism. It has an extremely compact design: a small cylinder that fits in the palm of the hand.
Curtas were considered the best portable calculators available until they were displaced by electronic calculators in the 1970s.
I’ve actually used one of these devices. One of my first jobs was working for an importer of business machines and the Curta was just one of a number of mechanical calculators they had kept in their archive of previously held stock. As I recall it was an extremely impressive, solid and beautifully engineered piece of equipment.
Images via Technophilic Magazine, where you can find out more about this amazing device.