Mystery clock, English, c 1935.
© Science Museum / Science & Society Picture Library
Art Deco clock made by Smith English Clocks Ltd of London. There is no visible connection to the hands of this clock, so how do they move? Three plates of glas are contained in the square framed metal surround. The front plate carries the painted figures, the rear plate is plain, and both are fixed. Between the two is a third plate which can move up and down through a total distance of approximately half an inch; a cogged hole in its centre providing the necesary ratchet movement to activate the hands.