Alexander Calculating Machine
From the collection of National Museum of American History. Free to download, adapt and use — no permission needed.
This is the U.S. Patent Office model for a lever-set non-printing adding machine. It has a wooden case with a curved metal front and back, and somewhat resembles an early cash register. It contains eight cogged wheels that rotate vertically on a common crosswise shaft. Each wheel is linked to a lever that extends from the front of the machine and is rotated upward to enter a number. The digits from 1 to 9 are stamped on the front of the case next to the opening for each lever, to indicate the digit being entered. Each large cogged wheel is linked to two smaller wheels. One turns forward, and gives the total entered. The second rotates in the opposite direction, and indicates differences. Each of the small wheels has the digits from 0 to 9 indicated around the edge.
National Museum of American History’s own description
