I have never seen a patina like the one on my Probus on any other coin. It is not like green crusties and seems to sit one the surface rather than being a patinated surface layer. It has a slightly greasy feel. It is not like any Jax treated coin that I have seen. It isn't easy to remove and I have tried a few techniques.
At the end of the day I believe the coin to be legitimate but the patina to be false.
Martin