Comptometer WM - War Model
c. 1940
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"The WM Comptometer was introduced during war years when material was at a premium and in general moved were made to conserve materials.  The earlier ones used steel that was perforated similar to the airfoil members on a planes wing. In the case of Comptometers however, it was not to reduce weight but to stretch the available material as far as possible.  Perforating the steel reduces its lateral strength so, to compensate, ridges were pressed along the length, similar to what you see in a trucks aluminum body to stop rattling in the wind. Numeral wheels were of lighter material and actually felt fragile although this did not appear to be derogatory to their functionality. The N/Wheels were black on yellow and yellow on black but I did not understand any significance in this other than to differentiate them from other models.

Plating was expensive and time consuming so to assist the war effort the plate was painted black rather than satin chrome. This conservation did not take place at the expense of functionality and parts that required close tolerance retained their quality." Ray MacKay.

Source: Ray MacKay

X-Number World