Addimult Addmaster
It is an Addimult Addmaster, serial no. 802422, from the 1950s. It is a virtually exact copy of the pre-war Addiator. It is mounted in a steel case which doubles as a desk stand. It can be flipped over to access the subtraction side.
David M Riches

Source: David Riches's Collection

X-Number World of Calculators