Underwood Olivetti Summa Quanta 20  
Written by Accutron on 2017-03-07  

Introduced in 1961, the Olivetti Summa Quanta 20 is a compact, motorized adding machine, designed for home and small business accounting tasks. The Summa Quanta 20 is directly derived from the iconic Summa 15 and Summa Prima 20 manual adding machines, famous for their four-way function joystick which selects between add, subtract, total and sub-total. The motorized Summa Quanta 20 replaces the joystick with a two-way toggle switch for total and subtotal, while add and subtract have been moved to the keypad. All Olivetti machines of this type were designed by engineer Claus Capellaro and industrial designer Marcello Nizzoli.

As with many other office machines, Underwood secured US distribution and marketing rights for the the Summa Quanta 20. While most of these Olivetti-manufactured machines are branded Olivetti Underwood, the machine pictured here is branded Underwood Olivetti.


Underwood Olivetti Summa Quanta 20 motorized adding machine, serial number 6143245.


Summa Quanta 20 adding machine, internal construction.

This article is part of the [Mechanical Calculators] exhibit.

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