If the bbls are good - thick walls, in proof, not dents, dings, bulges, etc - I'd say it's worth $2 -2500. I'm assuming it's an ejector gun.
Quality wise, it's probably better than a lot of guns costing far more than $2500. Heck, it's probably better than American stuff costing $20,000.
The problem is that it was made in Belgium by someone few Americans know.
Check out this Francotte for a comparison:
http://www.cabelas.com/cabelas/en/conten...erarchyId=11653That gun looks like it's in the same category as yours and it's a Francotte - a name guys know and want. That makes a big difference.
Without a name, Belgian stuff can be real hard to move.
OWD