How about probably no older than 1946? Found the/a patent:
#2542241, Feb. 1951, John Fors to New Britain Machine Company (applied for in 1946).
How about 8 "different" models:
front to back: New Britain, Fairmount, None Better, Precision-Bilt, Husky, Filson, Mustang, Blue Grass
The diagrams in the patent show the ratchets pictured in front with the screw thru the selector lever,
not the ones in the back with the pressed on lever.
Have to keep looking to see if there's a separate patent for the pressed lever models.