The 1939 Desch/Mumma Calculator

As described in Desch/Mumma interview with the Smithsonian
filed 1940, awarded 1952

As written Patent 2,595,045:

This invention relates to calculating machines and more particularly relates to an electrical calculating machine that functions to differentially accumulate items solely by the flow of electric energy and without mechanical movement of any parts.

In this novel calculating machine, selected numerical data is entered by means of the differential action of electronic devices into an accumulator comprising a plurality of denominationally grouped electronic devices, the selective operation of which devices during a plurality of data-entering operations causes the accumulation of data.

Calculator Front
Seen from rear, tubes are 885 thyratrons
Page from Desch copy of patent