C'mon, Dennis - if a guy's first two cars (in the 1950s) were 235 ci straight six OHV Chevs - and first truck was an OHV GMC 6 - you made that one easy.
WW 2
Every "screamin' GiMmy" '71 series engine in all their myriad applications, and the SCADS of Chev stovebolt sixes in alla' those duece and a halves included that tool in the first echelon maintenance kit,....by the end of WW2 they were EVERYWHERE on the planet.
With practice, a good hand can set up a bank of valves FAST with one of those rascals.
Can be used to set the racks on '53, 71, and early 92 series Detroit engines, too, IIRC.
GTC