Adding machine

This vintage mechanical calculator has a functional crank and an adding roll. It features numbered keys and operational buttons like Total, Non Add, Repeat, and Error. It's a heavy-duty piece of office equipment. A Comptometer (often misspelled as contometer) is the first commercially successful mechanical key-driven adding machine, patented in 1887 by Dorr E. Felt. It was used for rapid addition, subtraction, multiplication, and division, featuring a typewriter-like keyboard that added numbers immediately upon key release