That was almost certainly the Cinematronics "Space Wars" cabinet, which I saw here and there back then. I mostly remember one being in a bowling alley's arcade. It was a custom platform, not based on the PDP-1, but I'm not finding much info about it. It was two players only - there was no provision to play against the computer.

https://en.wikipedia.org/wiki/Space_Wars

There was also Computer Space, which was a very similar single-player game.

https://en.wikipedia.org/wiki/Computer_Space

While not the original setup, thanks to a bit of back-porting, you can play Computer Space on the PDP-1, too: https://www.masswerk.at/icss/