Just sold a 1957 Ithaca 37 for $425, shipped. It was a 16 gauge, 28" Mod, and was exactly how it left the factory-no choke thingy, no recoil pad, no weird bore machining, no rib, nothing. Used, but, not real hard.
Guy was happy to get it, and I had another guy who wanted it if he changed his mind. I think finding one, sans modifications of any sort, is getting to be a bit of a challenge. Oddly enough, I think the guy sought an unmodified gun, paid a premium for it, and then put a pad on it. I think it would have been worth less if it had a pad on it, and, I suppose, he made it worth less by doing that, but, he wanted it to be his gun after he got it.
So be it. It was a nice gun.
A rare gun has to be in demand for it to be worth money. Common guns (all pumps are pretty common) have to have a lot of demand to be worth any money. $425, shipped, is not a lot of money.

Best,
Ted