The Rotonde de Cartier Earth and Moon watch makes a virtue of being enigmatic. You would think it was a tourbillon that somehow got cased into what was meant to be chronograph, but this is of course wrong. Basically, the watch shows the phases of the moon on demand, thanks to a pusher at four o’clock. The pusher at two o’clock, in fact, controls the second time zone, hinted at by the 24-hour ring around the representation of the Earth.

As far we can tell, this is the only commercially available on-demand moon phase wristwatch in the world; it is certainly one of the few watches that cheekily and selectively obscures the tourbillon, making it an integral part of a far more humble complication… Although Cartier does not explicitly say so, such an on-demand feature typically requires the presence of a mechanical memory of some kind.

Speaking of that tourbillon, the execution is quite different to Cartier’s signature style. This is because Renaud and Papi helped create the watch to Cartier’s specifications. Interestingly, this is one of two Fine Watchmaking pieces from Cartier featuring a dash of outside flavour this year.

Limited to 50 pieces, the Earth and Moon clocks in at a hefty 46mm in platinum (price on application), which makes for quite a massive proposition.