Plus & Sumlock Mechanical Calculators
Plus 506/D

PLUS 506/D

PLUS model 506/D.

Decimal adder.

This has a direct action keyboard calculator of the "comptometer" type.

It is a model 506/D where the 5 denotes the abbreviated keyboard (keys up to 5), the 06 denotes the 6 columns of keys, and the D denotes a Decimal version.

185 mm x 180 mm x 127 mm. (7.25" x  7" x 5").

The angular style casing of the machine illustrated was introduced in 1958.

One of the more minimalist calculators made. Has 6 decades of keys, with each decade numbered from 1 to 5, so to enter a number between 6 and 9 two keys have to be pressed in succession in that column. The knob on the right is for clearing the total.

Made in England by Bell Punch Co. Ltd. and distributed by Sumlock Compometer Ltd.

The machine illustrated has serial number 506/D/815.357.


The bottom of the machine.


Many patents are listed on the label.

B.S. 1909 probably relates to British Standard 1909.

Capable really only of adding lists of numbers to 9,999,999, but capable of doing this quickly and accurately (and cheaply !).

Origins of Bell Punch Co.
Mechanical Calculator Days
National Calculating Service
Development of ANITA 1
Development of ANITA 2
ANITA is Launched
At work with ANITA
All Change at Bell Punch
ANITA Developed Further
ANITA at its Zenith
Sourcing from other companies
The Rockwell Connection
Demise of ANITA & Bell Punch
Mechanical Calculators
Early ANITA Desk Calculators
Transistors & Integrated Circuits
ANITA LSI Desk Calculators
ANITA Hand-held Calculators
Rockwell-ANITA Calculators
Calculators made by others
Advertisements & Brochures
Operating Manuals & Materials
Company Information
A Tour of Company Sites
The Technology Explained
Operating a Comptometer
Old Sterling Currency, £sd
Update Information
Getting in touch

Plus & Sumlock Mechanical Calculators

Plus Adder
Plus Adder B
Plus Adder D  (converted)
Plus Adder DA
Plus Adder S
Plus Adder SJ
Plus Adder ST
London Computator 509/S
London Computator 912/S
Plus 506/D
Plus 506/F
Plus 506/T
Plus 509/C
Plus 509/D
Plus 509/F
Plus 509/S
PLUS 509/SP Weight Calculator
PLUS 509/T Time Calculator
PLUS 509/Y Weight Calculator
Plus 512/S
Sumlock 912/F
Sumlock 912/S
Sumlock 912/Y Weight Calculator
Sumlock 913/S with Certopost
Sumlock Comptometer 993m
Sumlock Comptometer 993s

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Text & photographs copyright © 2002 - 2015 Nigel Tout, except where noted otherwise.