yeah, i'm aware of the Omega database. It's very handy.
Problem with fleaBay Omegas is many won't show you the case back inside or the movement where you can see the number. It's been a while since I was shopping for vintage Omegas (I learned all this the hard way, btw) but when I was, which was pre-crash I should say, $205 would not buy you a legit Seamaster. Heck, it probably wouldn't have even bought a Frankenwatch.
All that aside, I think sometimes over-focusing on the "legitimateness" of a watch is wasted energy. For $200, that's a handsome timepiece, and frankenwatch or not, it's a heckuva lot nicer and has a lot more character than a $200 quartz Fossil.