An interesting find on the #Nethack subreddit: someone obtained the 1993 Japanese release of the game "Nethack the RPG", which came with a full manual (guidebook), and they scanned the contents and put it up for all to see. I don't read Japanese so can't understand most of it (other than the proto-GPL license at the front lol) but it's also filled with anime-style illustrations throughout of the characters, actions, monsters and some items.
Reddit post w/ links to download sources: https://www.reddit.com/r/nethack/comments/1hq1bdq/nethack_japanese_guidebook_scan_nethack_the_rpg/
@greg "Nethack, the TTJRPG". :) That's awesome!