This little jewel of technology should boggle your mind. The purely mechanical device can add, subtract, multiply and divide. Curta Calculators were a post WW-II device commonly uses for calculations during Time-Speed-Distance (TSD) road rally. They are still used today for vintage rally where only mechanical clocks and mechanical calculators are allowed. It is a universal 4-function calculator that will literally fit in your pocket, that is, a mechanical pocket calculator, no battery and no computer chip. The user manual is called "Your Curta Calculator", a 24-page 367-KB pdf file.

The Curta Calculator was available in two basic models, Model I (8 x 6 x 11 digits) above, and Model II (11 x 8 x 15 digits) below. There were a lot of variations on style and trim, but they all work the same. Set the primary number on slides on the side and give it one crank. Lift the carriage on top and turn it to the desired power of 10, and crank away. Crank is in lower position for addition and multiplication. Crank is in raised position for subtraction or division. The ring loop on top is the clearing handle. Raise carriage and move clearing handle through one sector, white, black, or both to clear all.

In 23-1/2 years of production from 1947 to 1970 about 150,000 Curta Calculators were produced. The mechanical calculator in general was rendered technically obsolete with advent of the electronic calculator around 1970. Find more than you ever wanted to know about Curta Calculators at www.vcalc.net, along with lots of links do additional Curta web sites.

Production was started at April 1, 1947.
In 1966 CONTINA AG was bought by the firm HILTI AG in Schaan.
Production was stopped on November 1970.
CURTAs were sold until early 1973.
There are +/- 80,000 Curta I and +/- 60,000 Curta II machines.
150,000 to 160,000, maybe even more CURTAs were manufactured.

See YouTube video on the Curta calculator.