It also depends on what kind of proof of the gun's pre-ban status comes with it. To start with, what's the serial number?
PWA did not build complete rifles, so there are NO factory pre-bans. Thus, the only person who *could* prove that the gun was pre-ban would be the person who owned the gun on 9/13/94. Then, you'd need to get an affidavit from that person stating the gun's configuration (in detail), and that it was legally possessed on 9/13/94.
Of course, in 16 months or so, everyone's AR is probably going to be a pre-ban, which would make this just another old rifle, made by a now-defunct manufacturer, meaning no possibility of manufacturer support.
Just stuff to consider...