I have seen some blue/purple color on copper that I thought looked like NT. I suspect this develops over an extended period of time from prolonged...
@John Burgess Thanks for your recommendations. I've got a bunch of old wheat pennies to play with for fun. I've also got some MS70 that I have...
Sorry to resurrect an old thread, but this seemed like the best thread on which to ask my question. I'm a retired surgeon and have taken up coin...
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