All you have to do is run the case reference through the Omega vintage database. Google,Bing or what ever the caliber number. And get good pictures of all of it including a good pic of the dial. And than maybe you will have your answer. From the pics, can't tell if it an original dial, what caliber it is, and no pic of the inside case back, well at least not a full on shot. Other than that, it is in rough condition, if original, it would seem to need a crystal and service badly. Can't tell if that is dirt or rust pitting the case. And crown is differently wrong for this watch. in this condition $100-$200 max, assuming it is original of course.
Well, the dial seems to be OK, as well as the hands, but hard to tell with the pic. Nice 28X movement. That´s all we can tell with your pics!