We can’t really give you much more information than that stamped on the inside of the caseback. The reference number 135.012 only refers to the specific case so there are many different dial variants to be found for that reference. All Arabic numeral dials are uncommon but not rare and it’s not unkommon not to be able to find an exact dial match on the internet.
Valuewise: the caseback is well worn but the rest of the case seems somewhat unpolished. Later but original Omega crown and perhaps Omega signed crystal (hard to tell). The dial is of course the real drawback at it is quite heavily patinated (or damaged depending on if you are asking the buyer or the seller). Your name would suggest that you live in Norway so we have to price according to that. I would say around 350 euro (maybe 400 with good pictures) if it runs and keeps time.