Omega crystal insignia on vintage Seamasters

I'm talking early Seamasters from the 1940s and early 1950s such as references 2627, 2576/7, 2757, etc. My understanding is that Omega started including the etched insignia on the crystal in the early the 1950s. However, was this instituted across all the early Seamaster references around the same time or did some references receive the signed crystal sooner than others? Of those that did not receive signed crystals, is there a way to tell whether that crystal was born with the watch or an aftermarket replacement?

Good discussions but still wondering if and how one can tell if a non signed crystal was OEM. Also not much discussion on which Seamaster references first received signed crystals.