The other traditional complication that Cartier had completely rethought is the moon phase display. Imagine, once again, this complication and you will imagine a crescent-shaped window with a rotating disc with a little picture of the moon inside. But Cartier’s new moon phase watch cannot be more different. In fact, at just one glance, you might not even suspect it could show you the phases of the moon. Nonetheless, the Rotonde de Cartier Earth & Moon does have a few tricks up its sleeve.

Apart from the white gold Roman hour numerals and the etching of the planet, the dial seduces you with the mysterious beauty of lapis lazuli. However, curiously, on both sides of the crown you find two pushers – but this is not a chronograph. Pushing the button at two o’clock allows you to set the second time zone (24-hour rotating disc around the planet motif) while the button at four o’clock yields a delightful surprise. A paddle attachment swings out from under the four o’clock numeral, stopping just above the flying tourbillon but its exact orientation depends on the exact phase of the moon – full, half, crescent, gibbous, or new. Release the button and the paddle goes back in hiding.

Like the Rotonde de Cartier AstroCalendaire, this timepiece is also extremely robust and the risk of mishandling the moon phase mechanism is next to zero thanks to a Maltese cross system that only advances the moon phase when it should be advancing. With an open-worked back, Calibre 9440 is the result of a close collaboration between Forestier-Kasapi and complications specialist firm, Renaud & Papi (hence the tourbillon carriage is three-armed and not C-shaped). This watch is released in platinum (limited edition 50 pieces) and platinum with diamonds (limited edition 10 pieces), priced at €230,000 and €490,000 respectively.