Hi,
Regarding the 13amp/2amp combi. There was a jeweller's shop in Ellesmere Port that had several similar sockets. They also had a 13A & two fused 2A sockets but was rectangular and would fit in a standard twin gang back box. I'm sure they were made by MEM (Midlands Electrical Manufacturing, I think). I intended to ask for them whenever the shop was modernised - it was demolished instead
I find old plugs & sockets fascinating too, must get around to photographing mine sometime
I am interested in the 13amp sockets with various combinations of square & round pins made by Walsall, Britmac, Wandsworth, et al.
Cheers de Pete