Well, I see no evidence of the animal being a pewter, and given that you are in Europe, if you didn't buy it as a pewter (which it seems you did not), the chances of you accidentally receiving one are very slim, as I'm sure you realize.
As to the difference between the black albino (anerythristic) and the ghost corn, the difference is that the ghost is an anerythristic animal that is ALSO homozygous for hypomelanism. That is the only difference.
The problem is that it is very hard to tell the difference between darker ghosts and lighter anerythristics, especially as adults. As hatchlings, it's much easier, but even then it can be difficult, given the wide variation of the anerythristic gene in corns.
In point of fact, the ONLY way to determine whether that animal is a ghost is to breed it to a known hypomelanistic animal. If the resulting babies are hypo, your animal is ghost. If not, then the babies will all be non-hypos.
Of course, you have to take into account the possibility that the two parents (your animal and the one to which you breed it) are actually both hypos, but that they are homozygous for different, incompatible forms of hypomelanism. It is said to happen here in the States quite often, but I am unaware of how pervasive the problem is in other parts of the world. Are there multiple strains of hypomelanism known to be Sweden?
Rgardless, it is a nice looking animal, and I'm sure you enjoy having it very much! Good luck with it!