Plus & Sumlock
Mechanical Calculators
All of the mechanical calculators manufactured by Bell Punch were key-driven machines of the "Comptometer" type.
For more information about the history and families of Plus and Sumlock mechanical
calculators go to the page Introduction to Plus & Sumlock Mechanical Calculators.
Bell Punch Sumlock 912/S Sterling Currency calculator.
Bell Punch Mechanical Calculators
The early Petter based models were introduced by Bell Punch in 1939 under the name "Plus Adder":
- Plus Adder A - Abbreviated, 9-column, Sterling currency adding machine with farthings.
- Plus Adder B - Abbreviated, 9-column, Sterling currency adding machine.
- Plus Adder D - Abbreviated, 9-column, decimal adding machine.
- Plus Adder S - Abbreviated, 9-column, Sterling currency adding machine.
- Plus Adder SJ - Abbreviated, 9-column, Sterling currency adding machine.
- Plus Adder ST - Abbreviated, 12-column, Sterling currency adding machine.
These are all abbreviated keyboard models, that is they only have keys 1 to 5 in any column. To add a number higher than 5 then the operator has to press first one key and then another in that column which add up to the required number.
In 1940 a larger, full keyboard (with numbers 1 to 9 in each column), machine under the name "Sumlock" was added to the range, and a separate company, London Computator Corporation, Limited, was incorporated to deal more efficiently with the sales side of the calculators.
- London Computator Corporation 509/S - Abbreviated Sterling currency adding machine.
- London Computator Corporation Sumlock 912/S - Sterling currency adding machine.
In 1950 the name of London Computator Ltd. was changed to Sumlock Limited, and this in turn became Sumlock Comptometer Limited in 1961 when the British operation of Comptometer Corporation was merged.
Later Plus, Sumlock, and Bell Punch manufactured Comptometer models:
- Plus 506/D - Decimal calculator.
- Plus 506/F - Sterling currency calculator with farthings keys.
- Plus 506/T - Time calculator
- Plus 509/D - Decimal calculator.
- Plus 509/F - Sterling currency calculator, with farthing keys.
- Plus 509/S - Sterling currency calculator.
- Plus 509/SP - Imperial-Weight calculator.
- Plus 509/T - Time calculator
- Plus 509/Y - Imperial-Weight calculator.
- Plus 512/S - Sterling Currency calculator.
- Plusograph - Decimal/Sterling Currency add-lister.
- Sumlock 906/C - Decimal machine with 6 columns each of 9 keys and 7 column accumulator capacity.
- Sumlock 909/C - Decimal machine with 9 columns each of 9 keys and 10 column accumulator capacity.
- Sumlock 912/F - Sterling Currency calculator, with farthing keys.
- Sumlock 912/S - Sterling Currency calculator.
- Sumlock 912/Y - Imperial-Weight calculator.
- Sumlock 913/CP/S - Sterling Currency calculator with Certopost verification device.
- Sumlomatic - Sterling currency calculator.
- Automaticket Check Adder - Sterling currency calculator, with farthing keys.
- Comptometer 992
- Comptometer 993 - Comptomatic.
- Comptometer 993e - Electric.
- Comptometer 993m - Manual, Sterling Currency calculator.
- Comptometer 993s - Electric, decimal calculator with storage (memory).
For Plusograph see the Calculators made by others section.
A Selection of the Mechanical Calculators
Click on a picture for more details and more, bigger, pictures.
The early Plus Adders
