Generally speaking: 'PW' is before PoserWorld joined with Renapd's FairyWoods. 'pw' (lower case) is roughly about when PoserWorld and FairWoods joined together. 'pw2' seems to be the new Geometries folder I am seeing with my newer PoserWorld freebies (sorry, not a member so I don't know how true this holds to member items) This isn't absolute info but general info based on my records/folders.