It isn't that I think it might be PVC - in the pic it looks like minor corrosion to me. Corrosion can be caused by several things, not just PVC. Some types of toning can even cause corrosion and it doesn't matter what color it is. But that's why I was asking the questions - all I have to go by are the pics. You have the coin in hand, therefore you are more able to determine what is going with the coin than I am.
I can see what looks like corrosion in the pictures, but thankfully in hand it doesn't look that way to me. Even if it was corrosion, I managed to get this coin for 6 dollars when I was a kid. I just found a bunch of my coins from when I was a kid : ) Very pleased as these have a lot of sentimental value.