The Maine Penny, or Goddard Coin, was found in a Native American settlement in Maine in 1957. It could be a hoax, like the Kensington Runestone in Minnesota. Apparently it was found by a local resident among 30,000 other things.

You can read more here:

https://en.wikipedia.org/wiki/Maine_penny

http://www.ancient-origins.net/artifacts-other-artifacts/controversial-origins-maine-penny-norse-coin-america-020241#ixzz3YSS7Gv4P