Learning more about this is actually kind of hard. Unfortunately, there seems to be a lot of pseudoarchaeology concerning pre-Columbian transoceanic contact.
IMHO the most likely explanation is that it is either a modern-day hoax (that is, planted at the dig site) or a result of native American trading (After all, the fact that there were Norse settlements in Newfoundland is not in doubt - so conceivably, someone got the coin there and carried it south, that someone not being Norse)
It would be fun if a Norse settlement in the US could be proven, though. We'd be happy to incorporate you as a county of good ol' Norway.
So we already are an extension of Jutland, complete with morose temperaments and bad cooking.
I do accept that we have to distinguish between mythology and history, but lets analyse this according to scientific principles for a moment. If you have a theory and it accurately predicts what happens, we call that science. If the Aztec believed there were bearded white people living beyond the eastern sea that would one day come and conquer them, then it actually goes and happens, then I think it’s reasonable to take the origins of that belief seriously.
True :) Hadn't remembered this for some years, but your point above reminded me of it: There is a temple in Madurai (Tamil Nadu), or maybe another city in Tamil Nadu (which has tons of temples), where on the tower (gopuram) there are one or more carvings of a man (only the face) with a hat - like a Western hat. Had seen it as a kid when we went on a tour of South India. I remember my relatives saying that it could be that it depicted a Westerner, though the temple was made hundreds of years ago or more.
Besides that, there's plenty of evidence of pre-Portuguese presence in the Azores. There are theories that everyone from the Phoenicians to the Greeks to the Chinese discovered the island before Portugal did.