Produx pocket calculator

A very simple mechanical calculator of the Troncet-type, more commonly known here as 'an addiator'. This Produx was probably the main competitor to the Addiator. 

This particular little calculator likely dates to the 1950-ies. The protective sleeve is made of a plastic (PVC or vinyl) and it is made in Germany - West.

The Produx was manufactured mostly unchanged from the start around '28 (?). Even though the competitor Addiator became the generic name for these calculators, the Produx was made by Otto Meuter who was the inventor of these little devices. Addiator was founded by Carl Kuebler who licensed Meuter's patent. (May be that the royalties from Addiator sales then enabled Meuter to set up his own manufacturing.)

It is of very simple and low-cost construction. The Produx is quite compact at 4½ by 2¼ inch and very thin. The stylus made of rolled-up brass is a bit too flimsy; the tip is often broken off as it is in this case. A toothpick inserted in the stylus makes it usable again. Both adding and subtracting are on the front of the calculator, making it a bit more convenient to use than the original Addiator.

The sliders protrude through the bottom of the device, so resetting to zero is a simple pushing back - set it on the desk and push down.

These take a bit of getting used to, but then work surprisingly well :)