seamaster without bezel?

Hello! I have three questions about this old seamster. First, it does not have a bezel, but I do not see anywhere were the bezel would attach. Does this mean that this reference does is not supposed to have a bezel? Second, the crystal is not signed. Did all omega crystals have that etched signature in them, or perhaps, does this crystal predate the signing? Last, I see the metal compression ring on the inside of the crystal (I think that's what its called). How do I know what references are supposed to have that compression ring and which ones are not? Could that possibly be related to the lack of bezel?

I'm still trying to learn all I can about these vintage omegas. As always, thank you all so much for being willing to share your wealth of knowledge!

Thanks, both of you!