[Channing Greene, Sr]

Checking more closely I found the markings along the rib, which included the words "VULCAN STEEL". I should have seen that before I took it in for evaluation. In essence, I have a 12ga shotgun which has a Parker action, serial numbered, and a set of barrels, also Parker marked, but with non-matching serial number.
Since this is not a "complete" Parker, how does this affect the value of the weapon?
I have no idea why the barrels may have been changed without a change of numbers. Is there any source which would show that it had been returned for some reason, resulting in new barrels with new numbers?