Then in 1656, Dutch mathematician Christiaan Huygens made the first working pendulum clock, accurate to an error of less than one minute per day.

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"The atomic clock is actually putting out an electronic signal which is essentially analogous to the ticking of a pendulum clock... which might tick once every second or once every couple of seconds, " says Dr McCarthy.

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Skeleton clocks display the interior mechanisms of the timepiece, while mystery clocks, like the 1890 enamel and glass French timepiece showing a fetching young lady holding a pendulum clock, hide their mechanisms, thus presenting a mystery as to what makes them tick.

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