I can't even fathom competing companies today ever working with each other like this. Then again, Sony wasn't a competitor yet in the early 90s.

This is like the holy grail of videogaming.

Are there any other videogame legends and artifacts like this and the Atari cartridge dump[0] that could be lying around somewhere?

[0] https://en.wikipedia.org/wiki/Atari_video_game_burial

To be fair somewhere in the multiverse this did become the real Playstation.