All three pins are the standard shape, but are rotated by 90 degrees..
This style made by the Walsall company has pins of standard size and shape, but all three are rotated by 90 degrees, making it impossible to fit this plug into a standard socket.
This is a single pole fused version - double pole fused types were available, containing a fuse in both the line and neutral pins. The DP versions were used on centre-tap supplies, such as 110V arranged as 55-0-55.
A single metal socket outlet with switch. These can sometimes be seen in older installations, however the plugs and sockets are no longer made.
The back of the plug has 'Walsall' and 'Walsall Gauge' as the company also made plugs and sockets in the standard form.