"N_Cook" wrote in message
...

On practical joking, this was to wind-up my parents , when I was aged
about 10.
A syncronous mains driven/timed mantle clock . I was intrigued by this
little flipper/kicker thing that operated when you turned on the power.
If you disengaged it with a match, then half the time , when switching
back on, the clock would go backwards.

That reminds me of a clock we had when I was growing up. On the back was a
small wheel and you had to spin it in the direction you wanted the clock to
run when it was plugged in.