- Model J
final mass-produced shoebox model was the long-lived "J" with serial numbers
starting somewhere around 250,000 (earliest known serial is J-249,633, latest known is
J-394,374). It first appeared in February of 1926 and was clearly intended to replace the H-model and was set it off visually from its predecessors
by its green keys which replaced the traditonal black.
Altho the "J" had no major new features, many operational aspects were markedly improved and it received wide acceptance in the late "roaring 20s". The model was in constant production until the start of WWII concurrently with the newer electric (K) and "streamlined" (M) models. Many of the survivor examples were still in operation at major U.S. corporations until the late 1970s, a remarkable record spanning some fifty years of useful service"
Brooke W. Boering (aka Vagabondo) - The Comptometer Memorial Website
Source: The Comptometer Memorial Website