The difference is in the thickness of the sights “tenon” that fits into the slot in the slide.
Colt guns of that generation are NARROW tenon (Colt went to a WIDE tenon in the late 1980s). To know for sure measure the slot in the slide (or on the old sight). NARROW tenons are .058” thick, WIDE tenons are .125” thick (and Springfield Armory uses a proprietary “MEDIUM” tenon that is .088” thick)
Hardships are quickly forgotten. Intense heat, bitter cold, rain and snow, fatigue, and luckless hunting fade quickly into memories of great fellowship, thoughts of beautiful country, pleasant camps, and happy campfires.
Fred Bear 1902-1988