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It’s not an Omega crown. My suggestion is to post more photos so we can provide a more holistic assessment.
Have a look at the private watch sales forum here on OF. Vintage Omegas, including both manual and automatic wind Seamaster models, come up for sale with some regularity. You're much more likely to find a good watch at a fair price here.
<$300 on auction .
Just out of curiosity - What was the asking price?