Here is something I found when I was moving house that I never knew I still owned.
It's a switched double lamp adapter, these were pretty common here in NZ in the earlier days of domestic electricity supply:
As well, there was a small plug that fits into the light socket and you can run a 2 core flex to another light or small appliance, if the need arises:
The two side by side, for size comparison:
These devices were banned in the early 1980's here, mainly because of people lashing up all sorts of wierd looking installations, usually in home workshops.
The plug itself was banned because it could not ensure that the polarity would be correct every time it was connected, also there was no earth contact.