It seems to me that this is a WatchCo built or they used some new parts (bezel, hands, dial) that are "made in Omega" but ...
I love this model and you should be very proud to wear a restored (this is not a bad word for me) SM300.
I have one, no date, that I (my watchmaker in fact) did the rebuild using parts from WatchCo (bezel, insert, dial, hands and case back) and I'm very happy with the result.
The movement (tuned to the perfection) and case are original, as far I know.
Here is mine:
I believe that if Omega reissues the SM300 it will be a major hit.
Size, weight are just perfect.
Your post, with the great pics, just give to me an urge to wear the SM300.
It will be my tomorrow's watch, for sure.
Back to your watch, the only point (that is more a question for the experts) is the "Swiss Made".
All Omega vintage dials that I got from WatchCo (SM300, SM200 and Speedmaster) carries the "T Swiss Made T", despite the fact that they are Luminova.
Cheers,
Nilo