It's borax left on the metal by the way.
If PCGS is offering a reward still, which I don't know or I have never seen personally, they probably figured it out and stopped offering it.
The rest The residue is on the metal before it is hit with the die. The residue is "stamped" into the metal deeper than just the surface. That...
They are not sending in the whole box to get looked at. They are hand picking out a few select ms70s. So they are not spending $2500
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