1958 Portuguese India 1 Escudo - Haze Or PVC?

I recently acquired this BU 1958 Portuguese India 1 Escudo coin with nice luster. However, I noticed it has some kind of haze on it, especially evident when looked at an angle on the left side of the coin around "Republica". Not sure if it is a bit of PVC or some other kind of haze? I soaked it in acetone for 36 hours, and nothing changed.

So, any ideas as to what kind of haze this is, is there a chance it can spread to other coins in my binder? It will be stored in a 2x2 cardboard holder in a binder with pvc-free pages.

I can try to take better pictures if needed. Getting the camera to focus on the whole coin at an angle was challenging.

Thanks!