January 31, 2023
by Ariel Adams
Easily one of the most visually and technically impressive high-luxury watches of 2022 was the limited-edition Cartier Rotonde Masse Mystérieuse (debuted on aBlogtoWatch here). I got to see the Cartier Masse Mystérieuse watch at Watches & Wonders 2022, and the concept is thrillingly executed and deceptively simple. According to Cartier, the better part of a decade was spent developing the in-house caliber 9801 MC automatic movement. Despite the small size of the oddly-shaped movement, the mechanism nevertheless contains 435 parts. It also happens to be its own automatic rotor. That’s right, the main point of the Cartier Masse Mystérieuse is that the movement doubles as the mass that winds the mainspring. This is like the Cartier that Louis Carroll imagined.
Normally, an automatic mechanical movement would have a weight that is attached to the movement and oscillated in relation to the movement of the wristwatch on your wrist. This motion creates the kinetic energy that moves the half-circle weight, or simply moves the watch into a position where gravity does that job. As far as I know, the Masse Mystérieuse is the first wristwatch ever to fully make an automatic rotor out of the movement itself. Technically speaking, the concept sounds mad, but the execution is possible. This isn’t the first high-end timepiece that seems like the remarkable result of a strange wager someone took while intoxicated. (“Of course, I can design it! Just give me two  years…”) Let’s not pretend Cartier is solving any horological problems with a watch like this. The Masse Mystérieuse is all about art — but functional, mechanical art, so more of us like it.
Cartier doesn’t stop at the movement-as-rotor, though. The Masse Mystérieuse is one of a long line of “mystery dial” Cartier watches that delight enthusiasts like us. That tends to mean one or more parts on the dial have “mystery settings,” meaning that you do not visually know how they are attached. Sure enough, if you peer at the dial of the Cartier Masse Mystérieuse, you will see that it is not immediately obvious how the movement (and hands) are attached to the outer part of the case. This is achieved because the movement and hands are all mounted on a series of transparent sapphire crystal discs.
There are a lot of little surprises within the 9801 MC automatic movement. For example, it is designed so that, of course, the hour and minute hands in the center of the dial do not move, even though the movement itself is. That required Cartier to develop a differential system. The movement also operates under different pressures, and yet it maintains a 4Hz (28,800 bph) operational frequency with 42 hours of power reserve. You can read more about the innovation of the movement in the original Cartier Rotonde Masse Mystérieuse debut article linked-to above. The final decorative feature of the movement is the impressive level of skeletonization, which is, likewise, finished by hand.
While the Cartier Rotonde Masse Mystérieuse is not a small timepiece, it is not an oversized watch, either. The case is 43.5mm-thick in 950 platinum, 12.65mm-thick, and water-resistant to 30 meters. You can see how the watch looks on the wrist; the smooth lines of the Rotonde case shape help keep it trim, and the semi-bare dial lightens the load. The case has a red ruby cabochon crystal in the crown, and attached to the case is a gray-colored alligator strap on one of Cartier’s newer deployant clasps.
Wearing the Cartier Masse Mystérieuse on your wrist for any period of time is an interesting experience. It certainly has flair, but it is, in a lot of ways, a humble-looking timepiece for one that costs over a quarter of a million dollars. The watch even has a practicality to it. The dial, with its easy-to-read hour and minute hands against the conservative-looking hour and minute marker ring, makes for a rather decent daily wear. At the same time, the entire concept is very playful. It is hard not to shake your wrist around (which either makes you look angry or as though you are air-playing maracas) to enjoy the motion, as well as desire to show off the mechanical animation to onlookers. What I love about the Masse Mystérieuse concept is that even if it requires a sophisticated watch lover to understand how the movement works, even a child can understand what they are seeing and be impressed by the fun and ingenuity.
While others might come in the future, for now, the Masse Mystérieuse watch remains a limited edition of just 30 pieces in platinum. Cartier has been known to release popular high-complication pieces like this in various metals, but it certainly isn’t guaranteed. If I were a particularly well-funded collector, I would seriously eye one of these. But I would also make sure that there is a Cartier boutique in town, as a novel movement like this may very well need to go back to the watchmaker from time to time to remain in tip-top condition. Price for the reference WHR00078 Rotonde de Cartier Masse Mystérieuse watch is $274,000 USD. Learn more at the Cartier website here.