I've seen them for 400 up to 600 or 700 depending on the maker, shape, and function. If it is in good shooting condition, and is in average shape I'd say 450. Most of the Belgian made shotguns of the day weren't on the expensive side even when new, and they made a bunch of them. They do have brazed barrels instead of solder, which is a plus as they age. Hang the barrels on a string and tap them with a screwdriver handle. If it rings like a bell, the barrels are still fastened together well. If it goes "thunk" they are coming apart, which isn't good. I bought one similar a few years ago for 400 bucks and it shoots fine. Just because they are old doesn't always mean expensive. As I say, there were a lot of them made.