This doesn't apply to just Greyhawk supplements.
But if more ammunition needs to be issued, just mention that TSR ceased to exist in 1997 when they were sold to Wizards of the Coast, so TSR could not have had reprinted books in 2003, 2005 or whenever. Even is this were to have happened, common sense would dictate that
WotC would have had its name plastered all over the reprints.
Very ill-informed sellers. I had one of these guys question a 1st print supplement some months ago making sure it wasn't a 2005 reprint.
