I'm in United Kingdom and I don't come across U.S. coins in everyday life. Quick question on colouration on the Dime edge. I've noticed that the edge of the Dimes dated 1971 to 1983 have either a copper colour which could be the copper core showing through or is toned. Now I've received more coins of the same period in sealed mint cellos and they too have the same edge colour. Is that usual for Dimes?