Plus & Sumlock Mechanical Calculators
Plus Adder SJ
Plus Adder SJ
Sterling currency, key-driven ("Comptometer") type, with abbreviated keyboard (only has keys 1 to 5). To enter a number greater than 5 two keys have to be pressed in
succession in that column. The lever on the right is for clearing the total.
This is a very small machine of this type and can add up to just £999 19s 11d.
Probably one of the first Plus models, which were based on the Petters design that Bell Punch bought from that company in 1936.
Made in England.
The case is made of Bakelite.
As with the Plus Adder S, on the bottom is a list of patents, see photograph below. 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 almost certainly one of the first Bell Punch
calculators based on the Petters design that Bell Punch bought from that company.
