Aia, The Endless Dungeon is a Wee Warriors product like Palace of the Vampire Queen and Dwarven Glory. Search the forums for posts or threads mentiong "endless" and "dungeon" and you'll find some previous discussions.
The "afterglow" website has some information:
The Endless Dungeon - a set of cardboard tiles you could glue together into a number of floors and walls and use for miniature playing. An early issue of White Dwarf even reviewed this release and came to the conclusion that you were better off without the Endless Dungeon. My copy comes with cover art labeled Morno 1977 but has a copyright notice from 1975 inside it and a TSR distribution notice (the latter was crossed out). Apparently Wee Warriors repackaged leftover copies from the TSR printing with a new cover page. Or were there really two distinct printings?
http://www.stud.uni-hamburg.de/users/af ... index.html
Note: This information may be out of date in view of later Acaeum posts.
The Acaeum currently only covers Wee Warriors products that were sold by TSR including Palace of the Vampire Queen, Dwarven Glory, and the Character Archaic. Actually, I'm not sure why Endless Dungeons is not covered; the information above seems to indicate a TSR distribution notice.