That I don't know. Now sure how they would verify. Perhap it came from the vendor with a 'certificate of authenticity' for it limited edition run...like we have seen on TV so often.
At the time when the crystal skulls were being "discovered" authentication usually took the form of asking an expert their opinion. What do you do if the expert is the one presenting the object? You have to accept it as real because they have a reputation and you don't. Its all very annoying, but modern techniques have allowed institutions to circumvent this process for the most part.
But people were also so desperate for anything from the past that authentication was quite slipshod (lets talk Piltdown shall we?) and frauds went undetected for a long time (Piltdown again, and the skull for that matter). Given what was coming out of Egypt, Mexico, and China, the more spectacular the object the better. It was a grand show of oneupmanship.