JJ1 comes with a file “LEVEL3.020,” which for various technical reasons crashes JJ1 and J1E, but it’s really an early Diamondus map. (Perhaps intended to be the first level of the game, since its next level setting is LEVEL1.000?) I cleaned it up and stuck it in as Diamondus level 3. Fully playable in shareware versions of JJ1.
Actually, I’m including two versions of the level. The main one is updated to fit the released versions of SPRITES.000, SOUNDS.000, and BLOCKS.000, which all got changed between the time this map was abandoned and the time of JJ1’s eventual release. It also removes some stuff put in just to test various bits of code, since that wasn’t supposed to be part of the level, and alters a handful of events to reflect later code changes (invincibility had a fixed duration, waterfalls worked a bit differently, +15 orbs didn’t need to be shot and used a now-lost sprite when destroyed).
However, if you find and destroy the secret level sign, you can play the level exactly as it was released, changed only to make it not crash when opened.
Original design presumably by CliffyB; edited in J1E, J1LES, and XVI32