Brian is correct.....it can be used on copper, silver and gold supposedly WITHOUT having any impact on the coin itself...experience has been that it removes so much dirt that coppers can look "pitted" only because the MS70 has removed all the dirt from all the pits....like anything, copper is the hardest to do without ruining.....but this stuff does a great job on taking off surface dirt, stains, etc. I tried it becuase I was told this was what professional coin cleaners used.
