While I am certain it is environmental damage, it is best not to do destructive testing like scratching. Weighing it would be the best bet. Remember, the edge where you scratched it is where the copper core of the clad "sandwich" shows. Normally missing clad is only on one side. If it was missing on both sides leaving only the copper core the coin would be very thin and underweight.
Edited by lcutler
12/07/2019 09:53 am