Why Would NGC Certify This?

Are you talking about the greenish bits?

I think it is pvc contamination and not TONING.
I guess the guy who sent it in to NGC didn't request conservation. you would think NGC would have done it on their own.

Guess I should send mine in from my 7070, based upon that mine should be at least MS65.

It was graded because of who submitted it. The coins in the Stacks 57th St holders are for the most part, junk and to be avoided.

It has "gunk" on it. How you can look at a picture and divine that the gunk is poly-vinylchloride residue and not of some other composition amazes me. (From reading coin forums one would come to the conclusion that in the history of the world there are only two substances that come in contact with coins, especially circulated coins, is verdigris and PVC.)

I'd rather be wrong calling it PVC than wrong calling it something else. And I'm always open to suggestions regarding what could cause features of precisely the same pale green color and propagation pattern as I know PVC plasticizers do. Normal toning won't. Over the next year or two they will slowly darken and thicken on the Z-axis, ultimately beginning to resemble verdigris. Once that happens, the damage can't be undone. I'd rather know for sure before then.

This may be the only time I'm ever qualified to say this, Conder, but apparently I've seen more of this than you.

I posted this Bust half in another forum and made a comment about the PVC on it. I was told by another Bust half collector that he's heard/read that coins of these earlier dates were often kept in leather pouches that left wax residue on the coins that would also tend to turn the same color green over time. But I guess the only true way to know for sure would be to have a chemical analysis of the "goo".

I'm always willing to believe additional evidence. In this specific case, the color is appearing only on areas which might have contacted the wallet, the highest points. That would have appeared anomalous to me, also, if I were considering it to be a PVC infestation. Honestly, that's not where I expect to find PVC. I expect to normally find PVC at the junctions between letters/devices and field, and in nooks and crannies. Bad cases like the coin in the OP can show it in the open fields, perhaps where little nicks have made the original surface (minus patina) more accessible.

For your part, though, if it isn't wax residue it's eating away your coin...I don't see anything untoward on your coin's surfaces which alcohol or acetone would remove to the detriment of the coin's look. Might as well give it a shot. If the alcohol removes it, then it was wax residue.