I have a 'new' SM 300, similar to a Watchco but built by a local watchmaker from all new parts and have come across this bezel insert, which appears similar to the Luminova bezel on mine, but would seem to be tritium, due to the colour patina. My question; is it a genuine, NOS OEM item?

For comparison, my 'new build' SM300:

 

Here are the 5 main 165.024/166.024 vintage bezels

 

In short: no, its a fake reproduction insert. Nothing to do with Omega. It's made to look almost like the "watchco" replacement SL bezel, which again was made in the image of the almost similar vintage type - the no. 4 in the row out of the 8 "normal" types made.



Besides some small difference in the font, the main give away, is the missing lume on the 5 min. markers...and the fact that Omega didn't og don't make any loose inserts for the SM300 bezels.

Stay away...

 

Thanks. As I suspected.
The lack of lume on the 5 min markers, for this version, hadn't alerted me, as surely not all variations did have e.g. 'A' above. However, the fact that the numbers and min markers all extend right in to the inner edge of the insert had already alerted my 'spidey' senses.
These are way more tricky than Speedmasters, which are my main interest. I bought the new build because I liked it for a daily wearer, it was cheap, built by an Omega technician for himself, using all NOS parts (including the movement) and of course I didn't need to agonise over whether or not it was a 'franken'. 'It is what it is' and it's a seriously nice watch that I can wear without worrying about it.

 

Yes, Only 3 of the 8 types didn't have lume on the five minutes marker...all of which had straight "1" ... But again this type should have the lume...

Enjoy your "new" version...