Plus Adder S
Sterling currency, key-driven ("Comptometer") type, with abbreviated keyboard (only has keys 1 to 5). To enter a number greater than 5 two or three keys have to be pressed in succession in that column. The lever on the right is for clearing the total.
The photograph above shows a total of £123,456 17s 11d.
230 x 153 x 105 mm.. (9" x 6" x 4.1").
Serial no. S/A5416.
Made in England.
On the bottom, this calculator has lists of patents, and the three U.S. ones were taken out by Guy Bazeley Petter, with rights assigned to Petters, Limited, Yeovil, England (the internal combustion engine manufacturer). One of the patents had been applied for in Great Britain in 1923 and the other two in 1930.
This is one of the first Bell Punch calculators, which were based on the Petters design that Bell Punch bought from that company in 1936, see the patents list below.
The case is typical of the early models in being made of Bakelite. The mechanism of these machines operates on the downwards stroke of the keys and there is no interlocking between the keys to prevent more than one key in a column being inadvertently pressed at the same time.
Text & photographs copyright © 2002 - 2023 Nigel Tout, except where noted otherwise.
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