The pre- vs. post-64 distinction with Winchester is an easy one. But I've seen people tout Winchesters as pre-1952 (maybe '53) as well. What happened in 1952/3 that makes people feel that quality went down after that? I've got 2
pre-64 M70's (one a 1951 model, the other a 1958 model) and I can't see any significant difference between the two of them in terms of quality. In fact the 1958 will out shoot the 1951 all day long.

Just curious...
Bob

bobv, I tend to agree with you, but there are some subtle differences.

Early rifles had a solid bolt knob, no hole drilled in the end. They also varied in the magazine capacity, magnums holding 4 instead of 3 rounds. I am sure there are some other differences too, but can't recall off the top of my head.

Anything much earlier will put you into the transition period, where the safety was different. Prior to that was the pre-war model, where the rear bridge wasn't drilled and tapped for scope mounts.