The troncet (or addiator) is credited to J. L. Troncet of France, who invented the device in 1889. He called it his Arithmographe. (In actuality, his work was based on earlier designs that were first started by Claude Perrot [1613-1688].) It was used principally for addition and subtraction.

A troncet’s flat, mechanical, palm-held calculator had three main components: the part for the calculation, a stylus, and a handle to reset the addiator. By inserting the tip of the stylus into notches along a metal plate, numbers could be added by sliding either up or down strips of metal with numbers marked on them. No gears or inter-linked parts were involved. To “carry one” when the sum of two digits was greater than ten, the stylus was moved up to and around the top of the device.