Vintage Omega Seamaster and Speedmaster plexy (how to date them)

First of all sorry if I'm boring you with such things that you already know.

I'm trying to realize an Omega topic based on Speedmaster and Seamaster plexy.
There are different kinds of logo on the omega plexy based on which you can determine if it is correct (in term of year of production) for that watch.
(I have read of some very few examples with "no omega logo" too)

The first logo used until about '70 years (until last Speedmaster ref. with cal. 321 or the very first with cal. 861 and until ref. 165.024 in seamaster 300) look at the "feet" of Omega logo, they are straight::





The second one (starting from about '70 years) has little feet of Omega logo "curled":

I did'nt think there were several versions of the logo on the plexi!

Thank's for the scoop Marco!!

Well, then I checked :


Thanks, I didn't know.

Thanks mstango for this thread.

And i noticed that there exist an other type of Omega logo : (is like the first one (omega straight legs) but with longer legs).

I have a picture, but it's not a very good one ! (although we sense the shape) :



It's from an original plexi of a 105.003 in 245XXXX sn sold in 1967.

I don't know if there is a chronologic difference with the more common "omega straight legs" logo...
I don't think so, i have a friend with a 1963 105.003, also with its original plexi but the logo is like your example, i think it's just an other kind of Omega straight legs logo.


But you can notice that plexi until 1970 are flatter than the more recents :



crédit : did
left : 105.012 with a service plexi.
right : 105.003 with its original plexi.