Ed, to answer your question I highly doubt that they used a metal butt plate from a hammer gun made decades earlier. If someone wanted to have a metal butt plate added for some reason they would have asked for one in current use on higher graded guns. It is more likely the old style butt plate was added later by a person trying to dress up minor damage to the butt stock or to dress up a shortened stock. how long is the stock in question? Does it fit into a normal length? If it is 12-13" then you can safely assume it has been shortened, if it is 14" + it might be full length.