- Model F
|"Also arriving in 1914, (Starting SN 100,000), this machine was destined to
bring volume production to the F & T factory. SN 100,981 is the earliest known and
141,722 the latest. If machines were produced in strict sequence, production of F-models
would appear to have outpaced all previous models combined. It was in production from May
of 1915 thru the end of the decade, some five and a half years.
A major feature was the presense of the "Controlled Key" (introduced on the elusive E-model) which locked the keyboard when any key was not fully depressed. Since these machines were operated very rapidly by trained operators, the ability to detect a partial stroke AND allow for immediate correction without losing the running sum was most welcome by customers. It may well have been the principal reason for the great popularity of the "F" over its lifespan.
Again, the arrangement of oil holes was altered with this model, it having a single set of "bare" holes across the dial cover, an added set of "eyelet" holes just under the 1-row and 12 of the eyelet type above the 9-row with no holes on any side panels."
Source: The Comptometer Memorial Website