|"Model B - serial number 11973
The top register is the set-up register. Its purpose is to allow the user to verify the amount that has just been entered - it does not calculate.
The lower register is the result register, and functions exactly as comptometers do.
The 'space' bar at the bottom of the keyboard clears the upper, or 'set-up' register only. The lever on the side of the machine is a clearing lever, which clears both registers. There is no sub-total function.
Each keystroke adds directly into the lower register." Jay Goldman.
Courtesy of: Jay Goldman