Wikipedia Commons 5 5C Curta01
Very cool Curta calculator via jwz.

The Curta was a small, hand-cranked mechanical calculator introduced in 1948. It had an extremely compact design, a small cylinder that fit in the palm of the hand. It could 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.

Ok – who has one or has used one?