220 ranges were in the later parts of 1970, more or less end of Q3 thru Q4 and a few confirmed from Q1 1971. Range is in the 305-309xxxxx serials.... this one has probably had its bezel replaced. If it was bought new with that bezel in Dec 1972, my theory is that perhaps the original bezel was damaged while the watch was in stock and was replaced by the store prior to sale.
The correct bezel for your watch is a DON, which is worth a whole lot more than a 220 though, and the watch as-is has a lot of history, so I think you're best off keeping it and enjoying it
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