Acetone Won't Take Off My PVC!

i guess at some point it was in a pvc holder, but currently it is in a MYLAR holder, which contains no pvc

Looking at the rough area just in front of the date makes me think the PVC damage has eaten into the surface. I don't think there is much you can do at this point.

If it has eaten into the surface, you won't get it off.

PVC may be or not be guilty, it depends on where the coin has been stored. Coins can be affected by any number of other aggressive storage environments, where PVC cannot be blamed.

The clear PVC material used in the manufacture of album pages is composed of PVC with a softener (known as a plasticiser) to make it pliable.
PVC album pages over the long term, can affect coins in two ways:

1.) The plasticiser can leach out as a gas, which can give coins a foggy appearance, most noticeable on high grade silver coins. This fogginess may be removed with acetone.

2.) Over the longer term (usually years), there can occur a slow acid attack from the chlorine from the PVC, which will turn coins darker, the silver ones at a slower rate, and if left, will turn them black. This darkening will not be removed with acetone, because the coin has sustained a chemical attack by the chlorine.

The fogginess and the slow acid attack usually happen at the same time.

If you wish to store your coins in Mylar 2x2 cardboard holders as I do, use archival quality album pages, which are not made from PVC. These pages are more expensive to buy and may be harder fo find, but the expense is justified if you think your coins are valuable enogh.

The slides are not PVC/vinyl. I believe they are acetate, which should be safe for coins.

I had around 30 coins in these baseball card plastic sleeves, mostly coins of little value but I still wanted to take care of them. I left them in there for like 2-3 weeks and 2-3 of them had the green PVC slime on them. One has a nice big clump of it....... so it does not take much time apparently, lol. Fortunately I got the more valuable pieces out a lot earlier and those seem to be OK.

Can the PVC damage appear after a (clean, undamaged) coin is removed from a holder with PVC in it?

What is the safe use of acetone? I thought cleaning my coins was verboten...

If you use the Search Tab at the top, you should find many, many posts about Acetone. Not sure why we don't have a separate Forum for Aceotone though since it comes up over and over and over.
Back to that coins problem. From what you already have read, Acetone will not do anything further than what has been done. Also, consider that since it is a 1939 Phily coin, over 6 million made, if those spots bother you, simply look for one in better shape. An MS-64 or 65 should be less than all the solutions you may end up using to fix that coin.
However, if you look closely you should see that some of the outer layer of Silver is now damaged in those places.
IF, your really in an experimental mood, a dip in that stuff for Silver Jewlery at Walmart may help. HOWEVER, it also may ruin what is left.