I was thinking it might be something to do with a printer because that really looks like one of the old style printer ports. I did some Googling and I found this.
https://www.ecu-rc.nl/Control/8262/range-rover-classic-3-5-efi-v8-84477-d-prc-4764/?tid=1
Looks like it was a part for his Range Rover which makes a ton of sense now give the other stuff in the place.
Bloody hell, jackpot! .. and I thought it was a flat-bed scanner that was bolted down.
My Google-Fu is pretty legit. :)
My first thought was that it was an ECM but then I wondered if they were around back then? More importantly, why has it got my initials on it? PRC