It's hard to believe, these days, that at one time, clocks used to run off the mains, in houses.
An apprentice and I were re-wiring a house a couple of years back, when the question came as to what this wierd looking socket was in the lounge.
I knew as soon as the question was asked (being in another room), I said it was for a clock.
The young fella could not have given me a blanker look.
2 Amp circuit if I remember correctly.