The picture shows a coin which is graded MS 62 by NGC. However you can see green spots ( of PVC residue or ?) . My question is how this coin is eligible for grading? . As I know green PVC residue is a reason to not be encapsulated by NGC & PCGS. Thanks for clarifying.
That is correct, but what I see on that coin is almost certainly not PVC residue. My guess is it's verdigris. And since they cleanly graded it, I suspect I'm right.
Things develop after slabbing. I had a couple of PCGS coins (and really, it is any company) and saw PVC. Had it sent in by a dealer friend with a couple other things. I figured they'd crack it, acetone it, and re-slab it, but they declined. On careful perusal of their guarantee, PVC is excluded. I presume it is because it can show up later. So, I pulled up my big girl pants and bit the bullet. Cracked it out of a top pop slab and acetone'd it myself. Then sent it to NGC so it could go in a registry set there. I would have left it in PCGS plastic but as long as it was getting cracked I ended up sending it to where I have submitting privileges. PCGS Detail of the pvc: And in the NGC slab. I have the white balance a bit different in the two photo sessions. But you can see the green gunk is gone. In any case, it was a nice enough coin to preserve.
It is a real shame that PCGS does not guarantee against PVC. I will say from experience that NGC does: I bought a few Moroccan coins which had PVC contamination, and submitted them to NGC for appearance review. They conserved the coins, regraded them, and shipped them back - all for free.
Kind of hard to tell from the photo, but a few things that might explain why it got slabbed even with PVC damage: 1.) They didn't notice it or if they did, thought it was benign crud. I don't think verdigris is the correct choice of words since it is a modern issue. More like crud. 2.) The coin is perhaps worth so little in even in MS66, that a MS62 grade properly discounts the coin from a superb gem even if it is PVC damage. In other words, with or without the PVC damage only worth a few dollars. 3.) The individual who graded the coin has geopolitical reasons for despising the issuing authority, and the spots are actually authentic grader spit intentionally added to the surface.