There have been a number of cases of items out of place-time in North America. It seems that quite a few of these items relate to the Vikings, like the Kensington Runestones or the Maine Penny.... A Viking silver penny was found at a native American site dating from 1180-1235 AD. Initially the penny was thought to be an English coin, but was later determined to be Norse in origin and minted between 1065 and 1090 AD. What makes this interesting is that this is some 50 years after the last of the Vinland voyages listed in the Norse sagas.
Could it be that the Vikings explored further and longer in North America? Is this a case of conventional history being wrong? Could it be that the coin found its way from older Viking settlements to this one? Could this coin have been planted/dropped which makes it seem like it is from another time?