Dad's Mystery Object (Some like it hot)

(and some thermionic valves for Some Like It Hot for DDW's challenge.)

Really not sure what this piece of vintage technology is. It moved from Dad's shed to mine, and I'm hoping that it might interest the museum rather then move with us to another shed. One thing interests me though, is this an early example of an integrated circuit (an 'IC') given that it is a self contained circuit that plugs into something?

Meeting this morning, and a bit more poking and fiddling in the workshop. Powered up one of the BBC-B's and loaded Revs. Hmm, underwhelmed. Nostalgia isn't what it used to be.