The Cartier Masse Mystérieuse may not have been the watch of Watches & Wonders Geneva, 2022 that was the easiest to imagine wearing every day, but it was probably the single most interesting complication of the show (with some real competition from another brand, Van Cleef & Arpels, with its Lady Arpels Heures Floral). The Masse Mystérieuse is a watch that seems exceedingly improbable at first glance and it continues to seem even more improbable the closer you look at it. It’s an automatic watch which of course, means a winding rotor (or oscillating mass, as it’s sometimes called) but the trick with the Masse Mystérieuse is that the rotor is also the movement.

The fact that the phrase, “the rotor is also the movement” makes absolutely no sense when you look at it from an enthusiast’s perspective is just one indication of how surprising the watch actually is. The images from Cartier look like a Photoshop trick, with the movement/rotor apparently mechanically disconnected from the rest of the watch. The mind fills with questions: How does the winding system work? How does the crown function? How does the rotor manage to rotate and wind the mainspring while the hands remain correctly oriented?

There are, of course, technical answers to all those questions. The interesting thing about actually handling the watch, however, is that knowing how it works doesn’t do anything to dispel the sense of baffled wonder you get when you see pictures – if anything, the effect is amplified.

Part of the reason for this is that pictures are static and seeing the watch in the metal lets you actually see the movement swing back and forth between its panes of synthetic sapphire. If you’ve never seen any of the other watches in Cartier’s Fine Watchmaking Collection, which was started in 2008 and wound down considerably by 2018, you’re probably not familiar with some of the mystery watches Cartier produced, including a number of variations on the mystery tourbillon. Under Cyrille Vigneron, Cartier has tightened up its design language considerably and the company as a whole has benefited, but taken as intellectual entertainment (never mind the actual commercial viability of the project) watches like the Astromystérieux were very hard to beat.

The whole notion of mystery clocks and watches as horological entertainment to some degree relies on the owner not actually knowing how they work. If you go to a magic show (and it’s worth remembering that the inventor of mystery clocks, Jean Eugène Robert-Houdin, was the founder of modern stage magic) the quickest way to take the fun out of it is to try and analyze how an effect was created instead of going along for the ride. When Cartier began selling mystery clocks from the Paris boutique in 1912 they were indeed perplexing – nearly the entire body of the Model A mystery clock was transparent, with the actual movement hidden in the base. Cartier’s boutique staff were deliberately not told how the clocks worked either, so as to keep as many people in the dark for as long as possible.

The pleasure of mystery clocks and watches is equal parts intellectual and kinetic – seeing the hands change position over time is what makes a mystery clock interesting. And it’s the reason for the sense of amazement you feel when you see the Masse Mystérieuse in person. The movement of the rotor is considerably faster than the rotation of the hands of a conventional mystery clock or watch, or even the carriage of the Astrotourbillon (a mystery tourbillon with a carriage that rotates once per minute) and the speed with which it turns, combined with its somewhat random oscillations, makes it perhaps the most compelling mystery watch Cartier’s ever produced.

Alot of the time, transparent and semi-transparent watches suffer a little bit from being put on the wrist (especially if yours is a hirsute wrist). Skeleton watches often look more compelling off the wrist than on, depending on the design of the watch. The Masse Mystérieuse, on the other hand, looks great on the wrist – it provides the same visual excitement as the visible rotor on M.A.D. 1 Red, but with the bonus of the apparent disconnect between the movement and … well, anything else. At 43.5mm x 12.64mm, it’s a large watch, and with Cartier’s return, over the last few years, to designs and dimensions that represent classic Cartier, it’s not exactly a mainstream watch. The size, however, is the stage this piece of horological theater needs, and seeing it in the metal is proof that as good as pictures and video can be, there’s still nothing like a live performance.