Sumlock Sumlomatic Comptometer 912/S/6a/604.052.A

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Sumlock Sumlomatic 1959

The "Sumlomatic" was the final development of the Bell Punch Company's mechanical calculators. It is based on the motor driven dual-register machine, with the addition of a third register and a control mechanism to perform semi-automatic multiplication. The concept is described in Webb's US Patent 2956741, filed in 1955, but the machine did not reach the market until 1959. A full keyboard Sterling Currency "Comptometer" type machine with a multiplier register. According to an exhibition review in "Office Magazine" for June 1958: "The star on the Sumlock stand is the Sumlomatic. This is a new key-driven calculator with a multiplier register as well as the usual working register and store register. Digits for the multiplier (the lowest-register in the illustration) are set from the keyboard by means of a transfer button (seen on the right) which is also used to transfer digits from the working register to the store register. For repetitive multiplication by the same factor the multiplier register is provided (on its left) with a locking switch. The large key seen to the left of the board is the multiplier control. Whilst addition and subtraction can be in £ s. d., multiplying must be in decimals. Division is done by turning to a printed table of reciprocals and then multiplying. In busy commercial offices where several kinds of computation are done, the use of the Sumlomatic will undoubtedly lead to a daily saving of many thousands of key depressions as compared with previous models. This remarkable new model weighs 341b. and costs £330 [about US$900]."

The Bell Punch company did not manufacture any calculators until the 1930s when in 1936 the parent company, Control Systems, acquired the rights to the adding machines of the Comptometer type manufactured by Petters, Limited, of Yeovil, England and sold under the name "Pettometer".Due in part to the use of the old £sd Sterling currency and imperial units of measurement in Britain and the British Commonwealth, Bell Punch manufactured a greater variety of "Comptometer" type calculators than any other company. Information from

Our machine is in excellent condition and has a model number of 912/S/6a/604.052.A and was very kindly donated by Mrs Pauline A Toghill.
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Manufacturer: Sumlock
Date: 1959

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This exhibit has a reference ID of CH6728. Please quote this reference ID in any communication with the Centre for Computing History.


Sumlock Sumlomatic Comptometer 912/S/6a/604.052.A

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