If they're not marked one way or the other, how will you know that you're buying a pre-ban magazime when you're overseas?
Also, has someone taken apart their P99 high-cap to look inside for a tell-tale mark that denotes it either as pre or post-ban? Both a "pre-ban from Earl's" and a "pre-ban" from another source should be compared!
On the other hand, if it's there, I'm sure it would be encoded so as to minimize frauds.