Right??? @Cascade still in the mint cellophane too, crazy how sulfur from the mint envelopes gets through those seals.
The cellophane leaks. I'd rotate it around to expose the other half, put it back in the same conditions so the whole thing tones. Either that or remove it and put it into an airtite so it stays like it is.
Thanks @BadThad ! Yup, it's in the same envelope it's been in for I'm guessing the past 60ish years, so I hope the whole thing tones. (in hand, definitely silver not blue btw)
Manipulate it around so the other side is exposed. There must be a pin-hole or small crack in the cellophane.
I just bought this crusty 1939S for my set. It is my first 1939S and will fill that hole until I find a nice FB example in my price range (could be a long while) . . . . I will likely send in for reconsideration.
I am familiar with the person from which you bought this coin, based on its images, and I hate to ruin your excitement, but what appears to be beautiful toning on this coin will most likely turn out to be closer to environmental damage. I bought a similarly toned mercury dime from that same seller, as the images made the toning appear to consist of colors which in reality it didn't have.
Returns are accepted and I won't hesitate to send back if it does not match the pics. I'll let you know what I think of it in hand. I do expect a bit of crusty coin, not a rainbow toner. Did you return yours?