Resulta BS 9
The Resulta BS 9 and its older sister the Resulta BS 7 were made in the mid 1900s in West Germany. These adding machines were invented by Paul Bruning, and are capable of both addition and subtraction. The difference between the two models is the number of digits the calculators have to work with.
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AS7 Adding Machine (like sleek Resulta) $88 (source ebay wormel)
AS7 Adding Machine (front)
AS7 Adding Machine (back)
Komet Resulta-like (source ebay deuxlions)
Also check out the Precise Adder.
Resulta A7 aka Minerva (source ebay curtanl)