Bayonet fitting, angle adjustable lamp base, metal and bakelite(?)
Working, removed from attic largely because I was replacing some nasty old wiring and didn't want a non earthed metal fitting which is too big and gets in the way. Actually more robust that the holder I replaced it with, which broke almost immediately :(
Might be a match for something.
Vintage light bulb holder (Steventon OX13)
This offer has been gifted to someone and is no longer available.