Jaap's Mechanical Calculators Page


Olivetti Summa 15

Olivetti Summa 15

Olivetti Summa 15

The Olivetti Summa 15 is a manual adding listing machine with a 10-key keyboard. It has an 11-digit register, and allows 10 digits of input. Four function buttons have been combined into a unique four-way button reminiscent of a joystick. This button can be flicked with the thumb of the right hand just before you pull the lever. Depending on which direction the button is moved, a different function is performed - Total (∗ up), Subtotal (⋄ down), Subtract (- right), or Non-add (⊲ left). There is a small tab to the right of the keyboard which is used to release the four-way button if it was accidentally pushed in the wrong direction.

Olivetti Summa 15
Olivetti Summa 15
Olivetti Summa 15
Olivetti Summa 15
Olivetti Summa 15
Olivetti Summa 15
Olivetti Summa 15
Olivetti Summa 15
Olivetti Summa 15
Olivetti Summa 15
Olivetti Summa 15
Olivetti Summa 15
Olivetti Summa 15
Olivetti Summa 15
Olivetti Summa 15
Olivetti Summa 15
Olivetti Summa 15

There is cover that is easily removed, giving access to the ink ribbon. The machine takes a standard half-inch wide two-colour ink ribbon. The serial number is only found inside, etched into the metal base of the mechanism. The number of this machine is 366,286.

Olivetti Summa 15
Olivetti Summa 15
Olivetti Summa 15
Olivetti Summa 15
Olivetti Summa 15
Olivetti Summa 15
Olivetti Summa 15
Olivetti Summa 15
Olivetti Summa 15
Olivetti Summa 15
Olivetti Summa 15
Olivetti Summa 15
Olivetti Summa 15


Below is a video I made that demonstrates the Olivetti Summa 15.


The company was founded by Camillo Olivetti in 1908 in Ivrea, a village near Turin, Italy. Initially they made typewriters, but started on adding machines in 1934. Camillo's son, Adriano Olivetti, became chairman in 1938 and was responsible for the company's focus on innovation and design, and for the expansion of its international subsidiaries and sales. In 1959 it even acquired the major american typewriter company Underwood.

Even as Olivetti was making mechanical calculators and adding machines, it was also researching electronics, making Italy's first commercial electronic computer, the Elea 9003 in 1959. After the death of Adriano Olivetti in 1960, Olivetti's lack of leadership and the cost of the Underwood takeover caused financial difficulties, and the electronics division was spun off to a separate company and sold to General Electric.

In the 1970s a renewed focus on small electronics and transition away from purely mechanical machines allowed the company to survive, but the heavy cost of this transition again put the company in financial difficulties. Carlo De Benedetti bought a stake in the company in 1978 and managed the company through its recovery. They developed new electronic products, including in 1982 the first Olivetti personal computer. They did not leave mechanics behind completely, but used their expertise in the development of printers, fax machines, and photocopiers. In the 90s they moved into the telecommunications business, buying the majority of Telecom Italia in 1999, and eventually merging with it in 2003. Currently Olivetti exists as a subsidi


Olivetti's models were generally given successive model numbers, though it seems that some model numbers were skipped or never released, and some of the later model numbers were released out of order. They were also often given names depending on the general type of machine, occasionally with a suffix of a few letters or a word to describe the exact variant.

Model Names
Summa:Manual; addition, subtraction
Elettrosumma:Electric; addition, subtraction
Multisumma:Electric; addition, subtraction, multiplication
Divisumma:Electric; addition, subtraction, automatic multiplication, automatic division
GT:Grand Total, i.e. an additional totaliser register
CR:Carriage instead of a paper roll, often used for bookkeeping
Duplex:Two main registers
R or NR:Reduced capacity

Below is a partial list of models, taken from Rechner Lexikon. The production years are only approximate.

Summa MC 410×111940-19??The first adding machine Olivetti released
Elettrosumma MC 410×111940-19??
Multisumma MC 410×111941-1947Multiplier keys
Elettrosumma 1410×111946-1957
Multisumma 1410×111948-1954?Multiplier keys
Divisumma 1410×111948-1957Olivetti's first 4-function calculator
Divisumma 14 CR10×111948-19??
Summa 1510×111949-19??
Summa Prima 2010×111960-1974Manual
Summa Quanta 2010×111961?-197?Electric
Summa Quanta 20R7×81968-197?Electric
Elettrosumma 2010×111963?-19??Similar to Summa Quanta but rearranged buttons
Elettrosumma 20R7×81972-19??
Multisumma 2010×111964-19??First with fully automatic multiplication instead of multiplier keys
Elettrosumma 2212×131960-1966
Elettrosumma 22 Duplex12×131954-1966
Multisumma 2212×131958-19??
Elettrosumma 24 Duplex CR12×131954-19??
Multisumma 2412×131962-19??
Multisumma 24 GT12×13
Divisumma 2412×131956-1973
Divisumma 24 CR12×131960-1973
Divisumma 24 GT12×131962-1973
Tetractys 2412×131955-19??Like Divisumma?
Tetractys 24 CR12×131956-19??
Elettrosumma 2312×131966-19??Faster improved version of model 20
Multisumma 2612×131967-19??
Multisumma 26 GT12×131967-19??
Divisumma 2612×131967-19??
Divisumma 26 GT12×131967-19??
Logos 27-11965-19??
Logos 27-215×151968-1970Has an extra memory register and two totaliser registers.
Elettrosumma 1910×111970-19??
Elettrosumma 19R7×81971-19??


Gebrauchsanleitung für die Olivetti Multisumma 22 elektrische schreibende Rechenmaschine     (PDF, 13.6 MB or archive.org)
Ing. C. Olivetti & C., S.p.A.
56 page spiralbound booklet
148mm × 210mm

This is the German manual for the Multisumma 22 adding machine. The booklet has no copyright date, but this model was made from 1958.

Multi Summa 22 manual
Multi Summa 22 manual
Multi Summa 22 manual
Multi Summa 22 manual
Multi Summa 22 manual
Multi Summa 22 manual
Multi Summa 22 manual
Multi Summa 22 manual


Here is a selection of short articles about Olivetti's calculators.

1949 Efficiency op kantoor
1953-08 Administrative Management
1954-08 Administrative Management
1955-06-11 Bieler Tagblatt (Switzerland)
1956-10 The Office
1958-08 Administrative Management
1960-04 Business Education World 1
1960-04 Business Education World 2
1960-08 Office Appliances
1963-03 Business Education World

Long article about Olivetti's design
(1961-11 Industrial Design)

1961-11 Industrial Design 01
1961-11 Industrial Design 03
1961-11 Industrial Design 05
1961-11 Industrial Design 07
1961-11 Industrial Design 09
1961-11 Industrial Design 11
1961-11 Industrial Design 13
1961-11 Industrial Design 15
1961-11 Industrial Design 17


1926-05-01 Het Huisgezin (Netherlands)
1931-10-01 Der Bund (Switzerland)
1931-11-25 Der Bund (Switzerland)
1949-07-25 Neue Zürcher Zeitung (Switzerland)
1949-08-29 Neue Zürcher Zeitung (Switzerland)
1949-09-19 Der Bund (Switzerland)
1950-03-14 The Sydney Morning Herald (Australia)
1950-09-18 Neue Zürcher Zeitung (Switzerland)
1951-12-08 Eindhovensch dagblad
1951-12-22 Eindhovensch dagblad
1952-07-09 Eindhovensch dagblad
1952-11-01 Algemeen Handelsblad
1952-11-13 De Volkskrant
1952-11-22 Algemeen Handelsblad
1953-05-06 Gazet van Limburg
1953-06-17 Algemeen Handelsblad
1953-07-18 De Volkskrant
1953-10-12 Neue Zürcher Zeitung (Switzerland)
1954-07-24 Nieuwsblad van het Zuiden
1954-12-04 Algemeen Handelsblad
1954-12-18 Algemeen Handelsblad
1955-02-24 The Sydney Morning Herald (Australia)
1955-03-16 Western Mail (Cardiff, UK)
1955-03-19 Illustrated London News (UK)
1955-03-23 Derby Evening Telegraph (UK)
1955-03-24 Algemeen Handelsblad
1955-03-30 Western Mail (Cardiff, UK)
1955-04-02 Illustrated London News (UK)
1955-04-14 Neue Zürcher Zeitung (Switzerland)
1955-06-02 The Sydney Morning Herald (Australia)
1955-06-09 The Age (Melbourne Australia)
1955-10-29 Algemeen Handelsblad
1955-10-29 Illustrated London News (UK)
1955-11-05 Illustrated London News (UK)
1955-11-30 Algemeen Handelsblad
1955-12-06 Neue Zürcher Zeitung (Switzerland)
1956-04-17 The Sydney Morning Herald (Australia)
1956-04-18 Algemeen Dagblad
1956-04-18 Derby Evening Telegraph (UK)
1956-04-21 Illustrated London News (UK)
1956-12-08 Algemeen Handelsblad
1956-12-11 Het Parool
1956-12-15 Algemeen Handelsblad
1957-01-12 Algemeen Handelsblad
1957-03 Office Management
1957-03-20 Oberländer Tagblatt (Switzerland)
1957-03-26 De Volkskrant
1957-04 Office Products Dealer
1958-01-16 Algemeen Handelsblad
1958-06 Office Products Dealer
1958-11-27 De Volkskrant
1959-01-05 Oberländer Tagblatt (Switzerland)
1959-05-22 Algemeen Dagblad
1959-06-15 Newsweek
1959-12-21 Nieuwe Haarlemsche courant
1960-02 International Management Digest
1960-03-28 Neue Zürcher Zeitung (Switzerland)
1960-04-13 Die Tat (Switzerland)
1960-04-13 La Liberté (Switzerland)
1960-10-09 Neue Zürcher Zeitung (Switzerland)
1960-10-20 Le Nouvelliste (Switzerland)
1960-10-25 Oberländer Tagblatt (Switzerland)
1960-10-26 Algemeen Dagblad
1961-01 International Management Digest
1961-01 Office Products
1961-02 Office Products 1
1961-02 Office Products 2
1961-02 Office Products 4
1961-02 Office Products 6
1961-04 Office Products 1
1961-12 The American School Board Journal
1962-11 The Nation's Schools
1962-11-21 Leeuwarder courant
1963-04 American Engineer
1963-05 Business Education World
1963-05 The Catholic School Journal
1963-06 American Engineer
1963-09 Administrative Management
1963-09 Business Management
1964-02 The Office
1964-03 Nation's Business
1965-04-24 De Volkskrant
1965-07 Marketing Horizons
1965-08 The Office
1965-09-28 Algemeen Dagblad
1966-03 Nation's Business
1968-01-08 Staffordshire Sentinel (UK)
1971-01-15 Birmingham Daily Post (UK)


This is a selection of the Olivetti patents related to calculators.

PatentFiling datePublished dateNameDescription
CH 209,88404-03-193901-08-1940Ing. C. Olivetti & C.; Riccardo LeviQuiet printing mechanism
See also: GB 514,237
CH 210,23104-03-193902-09-1940Ing. C. Olivetti & C.Ten-key input with display
CH 215,17514-06-194001-09-1941Ing. C. Olivetti & C.Multiplier keys
CH 223,10131-10-194116-11-1942Ing. C. Olivetti & C.Direct total printing
GB 662,11831-08-194828-11-1951Ing. C. Olivetti & C.; Natale Capellaro; Teresio GassinoFour-way button
See also: US 2,545,649
CH 276,45529-01-194801-10-1951Ing. C. Olivetti & C.; Natale CapellaroAdding listing machine`with multiplication
See also: AT 172,028 B; DE 939,114; US 2,603,414
FR 988,26614-06-194924-08-1951Ing. C. Olivetti & C.Case suspension
FR 1,020,95526-06-195012-02-1953Ing. C. Olivetti & C.Ribbon reversal
CH 278,64017-03-195016-02-1952Ing. C. Olivetti & C.; Natale CapellaroAutomatic division
See also: AT 173,209 B; DE 915,510; GB 700,000; US 2,754,052
DE 1,042,27521-07-195330-10-1958Ing. C. Olivetti & C.Duplex calculator keyboard
CH 314,04430-07-195314-07-1956Ing. C. Olivetti & C.; Natale CapellaroDuplex calculator
CH 346,04923-09-195815-06-1960Ing. C. Olivetti & C.; Natale Capellaro; Teresio GassinoShortcut multiplication
See also: BE 571,491; DE 1,125,209; US 2,952,406


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