Hi Joe,
your paperweight is a PR402 which was a production item and not a trial.
I think the auction house are being disingenuous here!!! Or do I mean, they are lying!
The reason I say that, is that I contacted them about this very example and gave them a full explanation of the "S" on the base and its model number. They acknowledged my comments and accepted my reasoning. To later call it a "5" is very naughty.
There were a lot of this model PR402 that carried an "S" on the base. That suggests that either they were difficult to make (I can't see why this should be the case), or an inexperienced person made them ( also no evidence) or finally that they indeed had a lot left over from a production run. In my view, after having looked at several of these, I think this last explanation is the most likely and that your example is perfectly good quality sold off through the staff shop!!
Good luck with it and enjoy it,
Regards, Tony