I've seen similar guns at the Philadelphia, Pennsylvania gun shows with prices in the $800-1,000 range. They stayed on the dealers' tables a long time. I should note that most of these pre-dated the introduction of the Zoli over and unders that are now being sold as target guns. I think the Zoli name was a bit of a mystery to most people and buyers stayed away from the guns for that reason.
Having said that, I'll note that I have a 1960s 20 gauge set up for the American market of the time (single selective trigger, semi pistol grip, beavertail forend, vent rib, 26 inch barrels with nominal improved cylinder and modified chokes) that I've owned for at least 30 years. It's been a reliable performer both in the field and on the clay target range. It's a bit heavy (about 6-3/4 pounds) for a 20. The only issue I've had with it is that the ejectors aren't reliable if the forend iron gets at all loose from the forend. I don't know why and since the fix is to tighten the screw, I haven't had someone gunsmith the problem.
If the gun is in good shape, I think your friend will find it to be a good using shotgun, but not one that will greatly increase in value or have any serious collectors' interest. I'd expect to pay $600-750 American depending on condition and wood quality (the one I own has a pretty nice piece of walnut).
