I went into a shop in NYC six months ago and they offered me a watch that has been refinished as well as this one, for only $3500. I left before the salesman's shears could fleece me.
On the back there is this serial number, and a mark, where a 10 can be see. It could be a 10 micron plated?
At any rate it does not seem a back from an Omega case, usually engraved in the inside back
Best
FRANCO