Monroe's 'Full Automatic' calculating machine, 1922.
© Science Museum / Science & Society Picture Library
The design for this model was completed in 1922. It was the first machine to offer fully automatic multiplication and division. There was a keyboard setting mechanism, combined with a slide at the back for 'stepping' in the operations of multiplication and division. Monroe machines were originally the work of F S Baldwin, the inventor of the barrel calculating machine, and J R Monroe. Their first machine in 1912 began the trend towards full keyboard general purpose calculating machines.