Plug and socket combinations for electric clocks.
Clang Clock Connector plug and socket
Square shaped white plastic two pin clock connector by Clang.
Volex Temco 3 pin clock connector socket and plug
Square shaped white plastic three pin clock connector by Volex Temco.
MK flush mounting 3 pin clock connector socket and plug
Square plastic three pin clock connector by MK, list no. 4766.
Clock connectors were designed for one purpose only - to have a wall mounted electric clock connected to them. This could either be a directly powered mains clock, or for larger buildings, one of several slave clocks connected to a master clock elsewhere.
They are sold as a plug and socket set only, and are typically of thin profile so that the clock could be positoned directly over them, concealing the socket from view.
Clock connectors are still made by at least one manufacturer, but seldom used due to the prevalence of battery operated clocks.