Mechanical Calculators

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Wheel Calculators

Wheel calculators are fairly simple machines and can be compared to the Addometer type but with the wheels arranged vertically.  They are capable of addition and sometimes subtraction, and were made in robust metal versions to cheap plastic versions.

This page illustrates some typical machines:




Seven decade adding and subtracting machine.

Disk calculator with facility for addition and subtraction, selected by the lever on the left.
A number is entered by inserting a stylus in the depression of one of the moving disks against the printed number, and moving down to the bottom of the slot. The disk, having moved, then latches where it is left. This is repeated on the required columns, the total appearing at the top windows and the number just entered appearing at the bottom windows.
The number entered can be checked for correctness before all the disks are returned to their zero positions by pressing the lower lever on the right.
The total can be cleared using the upper lever on the right.

In the machine above 12,345.67 has just been entered, and has been added to the previous total to give a new total of 22,245.72.

119 x 152 x 117 mm (4.7" x 6.0" x 4.6").

About 1950s - early 1970s.

Made in Germany.

No cover.

With the cover removed.

Bowler Countess

Countess Sterling Adding Machine

£sd Sterling currency model.

Bowler Countess

Disk calculator providing addition only by dialling the required number on the gear wheels using a finger. Turning the little crank on the right clears the accumulator to zero.
These are a cheaper design than the Resulta type of disk calculator, shown above.

The machine above is marked Bowler Countess and is for the old British £sd Sterling currency, whereas the machine shown below has no name or manufacturer and is a decimal version.

135 x 170 x 130 mm (5.3" x 6.7" x 5.1").

This above model marked "Foreign Made" was launched in Britain at the end of 1960, and was distributed by Bowler Products Ltd., of London.

The price of the Bowler Countess was £10 10s Sterling [about US$28][1], which at the time was a considerable amount.

Decimal version

Decimal model.

These are fairly sturdily made but low-cost adding machines. There were also many cheaper all-plastic models from other manufacturers.




Disk calculator providing addition only by dialling the required number on the gear wheels using a stylus. Pushing the red lever at top-left clears the accumulator to zero.
This is a very cheap design largely utilising plastics.

140 x 135 x 100 mm (5.5" x 5.3" x 3.9").

Made in Italy, Brevetti Lanza-Savona.

Inside addipresto

Removing the cover shows that the majority of the components are made of plastics.

Inside addipresto

From the rear, showing the components which perform the carry.


  1. "Simple Adder", Office Magazine, January 1961, p59.

Vintage Calculators

Text & photographs copyright, except where stated otherwise, © Nigel Tout 2000-2024.