Those plates are reproductions and you can find them almost anywhere. E-bay for example. I have one as well and when I get a vin # for mine I'll have it engraved in the blank pad and stick it on the car somewhere.
Now, if the vin number that's on that plate is a legit number and the car is registered under that number one of two things happened. Either the owner purchased an "historical document" and passed it off as the title/registration for his glass car (which is fraud by the way), or he started with an original car that was way too far gone to restore and (assuming he legally owned the original) used the vin and title along with other original parts to register his glass car. Just because the frame looks new doesn't mean it isn't original and might actually belong to that vin number. One sure fire way to know is to check the frame for the vin number as it is stamped into the top of the frame on the driver's side near the spot where the firewall connects to the frame. Trust me there are a lot of cars out there with original frames that look brand new and some have glass bodies and some are Henry steel. It can be really hard to tell if the builder knew what he was doing.
Never pick a fight with an old man. If he is too old to fight, he'll just shoot you. - Anonymous