Lost history = partially unknown, we know is to cover or try to delete from history the massacre of a more advance civilization that was the nemesis of what now is the WG.
Originally Posted by DukeTheGold
Ancient Weapons = unknowned but we know that the ancient civilizations Poneglypths tell the location so we know they build them before they were erradicated.
Devil fruits origin, One Piece, Will of D, Sanji's left eye: unknown
all other we have a idea and some we just havent seen all the members of the group.