Mechanical Calculators

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Olivetti Elettrosumma 22-R
and other Olivetti add-listers

From the early 1940s Olivetti produced a series of compact "add-listers" (that is primarily for addition and subtraction, and printing a paper list of numbers entered and the results of computations). Here is a selection:

Elettrosumma 22-R

Olivetti Electrosumma 22R

Olivetti Elettrosumma 22-R £sd Sterling currency "10-key" add-listing machine (though has extra keys above the 10-keys for use with the non-decimal £sd Sterling currency).

225 x 380 x 195 mm (9" x 15" x 8").

Electrically powered.

This machine is for use with the British £sd (pre-decimal) currency and has ¼, ½, ¾, 10, and 11 pence keys above the normal 10 keys.  The additional complication of the mechanism for a £sd machine must have caused the designers a considerable headache.
The black keys with the white spots enter the same number of zeros as the white spots.

The Elettrosumma 22 was introduced in mid-1958, claiming "With a speed of 210 cycles per minute the Elettrosumma 22 is the fastest adding/listing machine yet produced."  It was priced at £89 15s GBP [about US$250].[1]

From Office Magazine, May 64[2] - "Costing £69 15s [GBP (about $195)], the Elettrosumma 22/R has all the chief features of the model 22 but has a reduced capacity of £999,999 19s. 11d. or £99,999 19s. 11¾d. entering, and £9,999,999 19s. 11¾d. totalling. ....  ... Its main operational features are: addition and subtraction, with credit balance calculation and signalling; multiplication by rapid repeat addition or subtraction; static memory (an amount can be held on the keyboard through a total or sub-total cycle if required); two-colour printing of all entries and results; non-print control; correcting key; and a simplified 'short' keyboard for easy learning and fast operation for anyone without previous training."

Inside Olivetti Electrosumma 22R

With the covers removed.
Inside is a 3-D maze of mechanical components.

Multiplication (and division) is possible with a "10-key" "add-listing" machine but is not straightforward and requires repeated additions.  The article "Sterling Currency (£sd) Multiplication on a 12-key Add-Lister" has instructions for performing multiplication on non-decimal currency amounts with a machine such as the Elettrosumma 22-R and gives an indication of the complexity involved.

One item to note in the above journal description is that the machine has "a simplified 'short' keyboard for easy learning and fast operation for anyone without previous training".  This points out that such a "10-key" "add-listing" machine can be operated easily without much training whereas a "full-keyboard" machine such as a Comptometer requires training in how to enter numbers and perform subtraction.


Olivetti were great proponents of small, elegant "10-key" mechanical "add-listing" calculators.

Their first adding machine, the "MC 4S Summa" was introduced in 1940, using pressure moulding, followed in 1941 by the "MC 4M Multisumma".


"The story of Olivetti is no less than the story of Italian industrial design.  At one time or another every great Italian designer has worked in some capacity for the company... ."

"Mario Bellini (b. 1935) ... has collaborated continuously with Olivetti since 1963, working on their entire product range. Bellini's chief work for Olivetti has been the 'Programma' microcomputer (1965), the 'Logos' and 'Divisumma [18]' calculators (1973), ..."

"One of the greatest of all product designers, Marcello Nizzoli (1887-1969) was the first and most influential of designers to work for Olivetti, ...  ... He went on to design a series of machines which have become 'classics' of modern industrial design: ... and the 'Divisumma 24' (1956)."[3]



  1. Office Magazine, September 1958, pp656-657.
  2. "Business Efficiency Exhibition", Office Magazine, April 1964, p282.
  3. Stephen Bayley, ed., "The Conran Directory of Design", 1985, Conran Octopus.

Vintage Calculators

© Text & photographs copyright Nigel Tout   2000-2020  except where noted otherwise.