Some of my favorite Omegas are the Seamaster chronographs that were based on calibre 321 from the late 1950-1960's. In particular the refs I can recall are 2884, 2907, 2947, 14360, 14364, 14904, 105.001, 105.004, 105.005, 145.005.
Here is a recent CK 2907 I acquired-
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