Okay a quick lesson in assessing a watch, as normally forum contributors will want to see what you think of it before chiming in.
Case: moderately sharp and still has observable chamfers on the lugs, which is an important element to inspect because case condition determines vale to a point. Second, and we can't do this here, it is important to match the model number with the calibre. The Omega vintage database is useful for this. You may like to ask for a pic of the inner case back for this purpose and check the database. Third, inspection of the movement . Is it clean? are there any signs of rust or scudding of the rotor. Are there gouges or scratches, possibly indicating replacements parts that have swilled around a parts drawer. Are the hues of the copper/beryllium plating the same, indicating original parts not swapped?
Then the dial: is it original? For that you need to acquire some knowledge on the signs of a redial and there are plenty of posts on the forum that will help you. In this case it is not easy to determine originality of dial and my take is that it may or may not be an earlier redial. Note, some of the spaces between the printed markers and printed minute index are not equidistant. So, it's too early in the appraisal process to definitively tell, and I would want to see a nice high res pic of the the printed lettering. (it may well be original, but seeing you are going to spend money on this watch, it's incumbent on you to be sure.)
Finally are the crown and hands original to this model. One way of assessing originality is to apply a general rule that Omega followed, and that is that minute and second hand only marginally touched the inner perimeter of the chapter ring. The style of the hands offers evidence, but the fact that the hands reach well into the chapter ring indicates that they are not original to the watch. Can't really see if this is an Omega crown, but this crown appears not to suit this particular model. So there you have it. Once have done an assessment of the watch, having ascertained the model number, and made a judgment on its originality, you can then search completed listings on eBay to see what similar models are fetching.
This is the barebones skill of collecting, essential if you are to make judicious purchases. Welcome to our world.
Cheers
Desmond