Back in the '80s,I was working at CompuPro in Hayward, CA. I was amazed that during a visit to a contract machine shop in Berkeley, called Graysix, that the turret punch/bender making the clamshell steel enclosures (CompuPro 10) was being fed paper tape for the G code instructions, and that the paper tape punch was programmed on a DEC PDP-8, of all things!
"...I'd love to get hold of a complete old computer like a PDP8..."
In the meantime there are always the PiDP-8 and PiDP-11 kits...
Video of the PiDP-8 being programmed via its octal switches:
PiDP-8 tour and demo