This is an extremely rare, small, mechanical calculator from 1939. Its inventor and patent holder is the Hungarian Endre Zolnay, a former car racer who developed several inventions in the 1930s. It was made in Hungary. The calculator was put into small series production in 1939, but due to wartime conditions, production stopped early. A few hundred were probably made, even fewer of them survive. (The factory numbering probably started with 1000) A real collector's item. One of the known pieces is kept in the Arithmeum in Bonn. It is in mint condition, requires expert inspection and commissioning. References: Detlev Bölter (https://www.boelters.de/Rechenmaschinen/index.html)