Bezel looks like later Omega bezel for 3590.50 or 3570.50 from late 80's-90's, with the accent and the shorter TACHYMETRE text.
Correct bezel for this SN 30.506.xxx would probably be B1 (DON), or possibly B2 (DNN) as the SN is on the borderline for the changeover. The current bezel looks good, but if you want a correct one the B1 will be expensive, but the B2 is more reasonable and "close enough" IMO, and easier to find.
speedmaster101.com good place to start