Ah, LGP-30! A few years back I had the chance to write some code for LGP-30 (emulated) as part of a CTF challenge: https://www.robertxiao.ca/hacking/defcon2018-assembly-polygl...
It’s such a weird architecture by modern standards - self-modifying code is the norm and you have to pay attention to the rotational speed of the drum. I can only imagine what programming on a real one must’ve been like :)