Hill Arithmometer. This Patent Office model for an early key-driven adding machine has a wooden case with two columns of keys. Each column has six wooden keys. At the back are two wooden discs. Around the edge of each disc is a paper slip with the digits from 0 to 9 printed.

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Size: 1936px × 1291px
Photo credit: © SBS Eclectic Images / Alamy / Afripics
License: Licensed
Model Released: No

Keywords: mathematics, medicine, science