J T Campbell Adding Machine. This Patent Office model for a finger-operated adding machine has four metal wheels set flat into a wooden case with a metal top (the fifth wheel is missing). Around the top edge of each wheel are ten short pins labeled clockwise from 0 to 9.

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Size: 1963px × 1273px
Photo credit: © SBS Eclectic Images / Alamy / Afripics
License: Licensed
Model Released: No

Keywords: mathematics, medicine, science