the new guns are Pre B like in that they have no firing pin block
actual early pre B guns had a smaller magwell, so some mags dont fit.
SP01 18rnd and the CZ factory 10rnd mags would work in one of these pre B.
CZ can get really confusing with nomenclature, because people tend to shorten it, or use with no context and that causes much confusion. like being in the middle of the woods and cant see shit.