Actually many archaeologists believe that the coin discussed in the reading is not a fake. They believe it represents genuine evidence that the Norse came into contact with Native Americans a thousand years ago.
First, the great distance of the Maine site from the Norse settlements in Canada. Well, many other objects found at that same Native American site had come from faraway places. Not just the coin. There's a perfectly reasonable historical explanation for these objects. The Native Americans who lived at the Maine site traveled great distances within North America. They were interested in obtaining objects from faraway places. The Native Americans could have reached the Norse settlements during their travels and brought the silver coin back to Maine.
Second, does the fact that we found no other coins at Norse settlements mean that the Norse didn't bring any coins with them? Not necessarily. The Norse didn't create permanent settlements in North America. At some point, they went back to Europe. When they packed for their return voyage, they packed up all their valuable possessions. They would have packed up all silver coins they had as well. So it's completely possible that the Norse had originally brought the coins with them to North America, but when they returned to Europe, they took the coins back with them.
Third, it's true that Native Americans wouldn't have viewed coins as money in the same way we do today or the way the Norse did in Europe. But the Norse probably knew that the Native Americans valued attractive or unusual objects. Silver coins might have been very appealing because of their beauty. For example, they could have been used in necklaces or other types of jewelry. As long as Native Americans found the coins interesting and beautiful, the Norse could have used the coins to trade with them.