What is a decent price for a Winchester Super X Trap gun in good shape?

I found one listed in a local website store for $495 obo. It has great looking wood and according to the gent who is listing the gun it they were built from 1974-1981 and he guarantees it works even though it hasn't been shot for years. My son is interested in it but I know nothing about them. Of course I DO realize that the gun needs to hit where you are looking so fit is very important so I want to make sure if he buys it and it doesn't work that he can get his $ back if he sells it.

Any known problems with them?

I can send you a link to the gun if that would help.