Hi Mark.
Three things weigh against this one:
1. The crystal is done for. The lines you see on it are due to shrinking because of age - they cannot be polished out.
2. The crown is an incorrect replacement.
3. The worst bit - note how the lugs are slightly "soft" in appearance? And how they seemingly are darker at the ends? This is due to overpolishing; the colour change is the base metal peeking out from the polished away gold layer. Unless a watch is very special this will be a deal breaker for me every time and it kills value like nothing else.
Finding a good vintage Omega at your budget is not impossible at all and you have two options - study the subject more than a little bit, bide your time and seek out the deals that aren't completely obvious
OR be plain, blind lucky. In both cases I'd stay away from Chrono24, if I was you.
Here is some inspiration:
https://omegaforums.net/threads/2017-what-omega-did-you-buy-for-under-500.51171/Click to expand...