|World of Greyhawk Adventure Series (WGA1-4)|
WGA1 - WGA3 form the "Falcon" subseries; each include fold-out cardstock buildings.
WGA4 Vecna Lives! remains one of the most popular AD&D modules
ever. It involves high-level mages, artifacts, and evil demigods,
and you really can't go wrong with that combination.
None of the modules have any distinguishable printings.
Thanks to Norbert Jakobs for the scan of WGA1.
Auction values on WGA1 - WGA3 seem to be rising, though the modules themselves apparently did not sell well. WGA4 already goes for very high prices (probably due to its popularity rather than any actual rarity).