The art of illusion fascinates adults and children alike. We are all spellbound when magicians deceive the eye with slight of hand and deft trickery, believing they achieve the impossible while knowing perfectly well that it is just magic. Maurice Coüet perfected the art of illusion in the mystery clocks that Cartier offered, beginning in 1913 with the Model A. Based on the 'pendules mystérieuses' from the 19th century, a selection of which was exhibited at the 1878 Exposition Universelle in Paris, the mechanism of these clocks is hidden in the frame such that the hands seem to float in space without any connection to the movement. Rather than moving by conventional clockmaking techniques, the hands are set into two rotating crystal discs with toothed metal rims that are propelled by gears in the clock case.

Since every part of the clock was hand-made, each one took originally from three to twelve months to finish; employing not only the watchmaker but also the designer, the 'orfèvre-boîtier', the enameler, the lapidary, the setter, the engraver and the polisher. Even with the help of modern technology, it still takes seven months to complete a clock such as this.
Cartier sold the first issue of the Model A to J.P. Morgan, Jr. in 1913, at their New York store. These elegant clocks with their clean, sleek surfaces and bejeweled hands have been favourite gifts to notables including Queen Mary, who received one in 1924, and Joseph Stalin, who was presented with one by General Charles de Gaulle in 1945.
More recently, Christie's Paris, 6 June 2002, lot 195, sold a Model B mystery clock, circa 1927, for the record price of $372,632.

Cf. Hans Nadelhoffer, Cartier: Jewelers Extraordinary (London 1984, pp. 251-254; Jader Barracca et al., Le Temps de Cartier (Milan 1989), pp. 302-303.