One more thing. Why I don't believe it is a hoax. This way it turns out into conspiracy theory. Secret powerful organization forge Roman artifacts in Americas, and keeps an eye on it's members then they will not tell anyone about their activity.

Still, there are no answers about that above artifacts, which are particular cases. The theories that it might be hoax or accident are just speculations unless there are scientific evidences of this artifacts being forged, that do not present.