I’ve mentioned that I collect books by the sf small press Gnome. Gnome was infamous for never (after their first book) removing the “first printing” designation on its titles even when it was obvious that a later second printing of different size and paper was released.
Asimov’s Foundation and Empire was one of these. A second edition using cheaper, thicker paper necessitating larger boards and a new dust jacket is acknowledged by all authorities. Some even recognize that the fat later edition comes in both green boards and red boards. But no one ventures an opinion on whether these were simply different bindings of pages printed earlier - which Gnome did regularly - or were a second and a third printing, probably because nobody had them to look at together.
But I do. One difference is immediately apparent. The page edges have alternating dark and light bands designating the signatures. All the pages are trimmed: they’re not deckle edged.
I don’t understand how a separate binding of the same original printed pages would produce this effect, but I’m not an expert on printing techniques.
Searching gets me nowhere. Any paper mavens in the house?