I think I have an error coin, it is a 1980 US dime copper planchet weighing 2.31g as per pics. It's heavier than a normal dime and it also seems like the edge of the rim is a little bit thicker. I looked into 1980 US dimes minted in Philadelphia and at the time they were also minting foreign coins. Is it possible that it was accidently put into a foreign copper planchet? What do you think?