I have to aggree with CF,,the true market value has many factors. Including condition(of course) and market area,,if all you know are centerfire modern shooters,,,,well they'll give you but little for it because like yourself, they won't shoot it.
I know a feller that owns and shoot's one of those. He's a top competitor in bp shotgun shooting. It seems "he say's" that the stock cut, fit, and balance is the same as the modern beretta shotgun he uses for trap and skeet comp.
I do remember him saying he had trouble with the lock spring on the left side,,and it was a 120$ repair? Parts were hard to find.?? Anyways,,in the right market you might have 3-4 hundered there for trade( I'm not a gun expert!) I think there is a forum here for "CowBoy Action" shooting. they might help,,good luck