Very RARE Foundation Trilogy 3 Book Set Isaac Asimov Doubleday Science Fiction

And they also state a "T28" Gutter code indicates the book was published in 1978. However, no other publishing information is available which demonstrates the book set's rarity. Here, Foundation has a gutter code of "O27";Foundation and Empire has a gutter code of "N22", whileSecond Foundation has no gutter code.