In Reply to: Parts catalog errors.... posted by Farmer Dan on February 10, 2019 at 08:58:46:
Having spent several years writing and proofing automatic transmision service manuals for GMs Hydra_Matic Division, I can tell you that even with all of the electronics an proof reading that we did, "stuff" still got through and into print. Sometimes a dealer bulletin had to be published to correct or "update" information.
Just thinking about the lack of computers and all of the manual inputs and reviewing required for manuals 60, 70, 80 years ago, boggles my mind.
As for the proof meter/tachometer/speedometer: it is all of them. Hours of operation at a given rpm, engine rpm at throttle setting for PTO, ground speed based on gear choice and engine rpm. Whatever your need to know. It could also be called a Hobbs meter as in an aircraft. I thought it was quite ingenious for the time.