[Lucien Nunes]

The sleeved pins were a rarity, offered as an extra feature by a few manufacturers including Sanders and GEC. They were also used on the Wandsworth proprietary gauge, where the switch was operated by inserting the plug. Shuttered sockets existed and I believe the sockets offered by Sanders concurrent with these plugs were indeed shuttered. Various other safety features were introduced ad-hoc, such as proprietary interlocking systems that usually captured the earth pin while the switch was on, fuses - both cartridge and bare wire in SP and DP configurations, and handshields that kept fingers well away from the pins.