detecting a cleaned coin

Well I suppose it would depend on the specific coin in question. But take Morgan dollars for example, even well worn examples can still be identified as certain VAMS due to strike diagnostics. And this is true with just about any type of coin. But could a coin be worn enough that it could not be positively identified as being genuine ? I'd have to say yes. But if it were, then it would simply not be declared genuine.

Ehhh, yeah some may "think" that. But I don't think it is any more true now than it ever was. Take the Omega Man for example. Forty years ago he was able to produce counterfeits that fooled just about everybody. It was only with microscopic examination that his coins could be identified. And even then, only because he signed them. Had he not signed them, they arguably would not have been identified.

So is it possible ? Yeah, it's been possible for many, many years. But is it likely to occur in large numbers ? I highly doubt it because it sure aint easy !

I doubt that would do much good. Ya see, good counterfeits are made using the right materials, gold or silver alloys of the correct fineness, and of the correct weight. And the only thing that X-ray crystallography or an XRF machine can do is tell you if the metal is the correct alloy.

The only way to positively identify counterfeits is with strike diagnostics. And so far at least, except for the Omega Man, nobody has ever done it. And even he got caught due to his own ego.

edit -

I would add something else. Whoever it was that made the micro-O counterfeit Morgans managed to fool PCGS for a while and they slabbed the coins as genuine. But they did not fool everybody, NGC for example refused to slab the coins because they were not convinced they were genuine. And they turned out to be correct of course.

And there have been a few other examples of counterfeits slabbed as genuine by the TPGs, but they were all caught eventually and the mistakes were admitted, and the coins bought back.

But those are all exceptions to the rule, and they are few in number.