Authenticity check on a vintage Omega I found in market place

It appears to be in decent shape, and might be a good watch for you. Genuine, but not an Omega calibre of movement that is highly sought after by most Omega collectors. Made at a time when Omega was grasping at straws, trying to stay in business. Shortly before they pulled up stakes as a maker, and sold out to the Swatch group. So if you are planning on flipping it, it may be a tough sell.

Looks like a reasonably nice late 70s constellation. Crown is obviously wrong, as is the seconds hand. Gold Plated (according to Omega: https://www.omegawatches.com/en-us/watch-omega-constellation-omega-pn-166-0228).

Because of the time frame, it isn't a particularly high quality watch, but a nice enough model itself.

The NICEST one I found that has sold (these don't sell recently) was about $450, though it was effectively NOS, where as this is in significantly worse shape. Case is nice but worn, Crystal needs some TLC, and as I said, crown and second hand are wrong. So I suspect this is 'worth' high $200s at best.

That said, a lovely watch that if you got for a good deal, would be lovely to wear until it dies without-a-service (that is probably not worth the cost).