Correntator (right # 029823 left # 048643 , ca 1925)
Continentale Buro_Reform Jean Bergmann (CBR), Berlin, Germany
dimensions...........7 x 10,7 x 0,3 cm
weight..................100 g
material................brass
digits ...................9
single sided
including a pencil (r)
There is a metal grooved plate that flips from addition to subtraction.