The "bizzare" things are cool. I have some sockets and pendant switches like that porcelain green one. I've never seen a tap (northwest of the green pendant switch) yet with 2 edison bases and the plug tap in that configuration.
I think a lot of people reading this will already know, but the round-pin receptacle shown as India/South Africa on that dist. board is the old BS546 15-amp outlet, also once the norm in the U.K. and still widely used here in theatre lighting.