Yes that 300 still haunts me, loved that watch and ended up having to break it for parts... ...a costly exercise all around!!
The first Oyster from 1931 already had the crown on the dial and had different hands. Even the case and crown look different. Is yours even a much earlier model?
The first (manual wind) Oyster was from 1926. This is a late '30s bubbleback (automatic). There were certainly many dial and hand variants. Rarely the coronet didn't appear on the dial, especially on this type of mirror track sector dial. Cf. this other of mine:
Evening swap and another new strap trial. Newly resurrected Lemania ref 912-5 caliber 3000 suits it rather well IMO.
This one is a result of quick action after reading "Recommended Omega Vintage Watches on eBay" .... thanks Mike!
Snap (32.2M mine; same model). I'm speculating that it actually dates from late '71 or so.. Would be interesting to know if the new Moonwatch Only book knows when the highest recorded serial for this model (32.8M) actually dates from...