Felt and Tarrant Comptometer, best adding machine.
Friends and clients Pete Underwood and his wife came into the play pen today, sporting a gift that they knew I would like.
This machine is a calculator. It can add and subtract rows of numbers far quicker than anyone using a modern calculator today. It’s beauty is in the fact that it’s data input is arranged in columns and rows. Each column has keys one to nine. Every time you press a key, the numeric value is added to the accumulator display at the bottom. Let’s say you wanted to add 4,634 and 6,276. You would arrange 4 fingers of your hand over keys 4634 and press in one go. Then do the same for 6276. The answer would appear in the display at the bottom. Two hand motions as opposed to ten finger presses on a calculator…
Comptometer operators were well trained and would command good salaries. They would look at a ledger book and touch type row after row of figures, like sight reading and playing a piano.
These machines started appearing in the late 1800s and were still produced into the 1970s. In the ‘60s Anita Sumlock made electronic versions, using valves, nixi display tubes and digital Decatron counting tubes. Brilliant!