The clever engineering of a mechanical watch is typically hidden behind a dial, but it's not particularly mysterious. That is, unless you find that the hands on your watch keep the time while appearing to float midair above the dial with no visible connection to anything else. This is the head-scratching but captivating effect of a "mystery dial," and it's not only fun to observe but has a fascinating story behind its invention.
The mystery dial seems like what you'd get if you combined a watchmaker's skills with the showmanship of a professional magician. That, in fact, is exactly how it came to be: In 19th-century France, Jean-Eugène Robert-Houdin performed feats of conjuring, slight-of-hand and all manner of illusion. He's been called the "father of modern magic" and was the inspiration for the famous magician Ehrich Weiss to adopt the stage name Harry Houdini.
Before he became known for his performances, however, Robert-Houdin followed in his father's footsteps as a watchmaker. It would seem he was seeking a bigger reaction than merely what an elegant timepiece could elicit, and this would manifest in his magic performances as well as objects he created.
Robert-Houdin was from the old-school generation of watchmakers that hand-crafted every clockwork component individually. He created automatons of singing birds, dancers and robot-like figures which would draw and write on paper. They were calculated to astound, just like his magic. In fact, the mystery clocks were themselves akin to one of his tricks, as he'd actually take them on stage as part of performances.
Not only were the hands of Robert-Houdin's mystery clocks apparently not attached to anything at all, one could see right through the dial to the other side with no clockwork visible. In fact, [SPOILER ALERT] they were mounted on clear discs with concealed toothed edges. The clockwork was also hidden (for example, in the clock's base), and the hands seemed to be turning entirely on their own.
Watches or clocks that produce a similar effect are now known to have "mystery dials" regardless of where the mechanics are hidden or other factors. Though Robert-Houdin is credited as the inventor, Cartier is arguably best known for the exotic mystery clocks they created starting with the Model A in 1912. Later in the 20th century, some would apply the concept to wristwatches, including Longines, LeCoultre, Vacheron Constantin and Zodiac.
The history of Robert-Houdin and the mystery dial makes such watches much more than a mere gimmick, and knowing how they work doesn't ruin the effect — it arguably makes it even more interesting. Today, this type of watch is rare, but there are some recent examples keeping the unique concept alive.
The Astrographic came out in 1969, and seemed to reflect the space-age mindset of the time in its design and mysterious dial — some even featured high-beat, 5Hz movements. The modern company brought it back in the 21st century, but today even the modern versions can mostly only be found second-hand. It's about the most affordable modern example of a mystery dial watch, but vintage ones can be even more accessible.
Konstantin Chaykin Levitas
This Russian independent watchmaker is eccentric, wildly inventive and quite brilliant — he probably would have gotten along well with Jean-Eugène Robert-Houdin. His Levitas watch features a clear dial with floating hands and is meant as a tribute to Robert-Houdin.
Rotonde de Cartier Mysterieuse
The Rotonde de Cartier Mysterieuse watch is cool, in part, because it references the brand's history making mystery dial clocks. The brand also executes the concept with its typical Cartier panache and offers it in a range of variations, from some with more traditional looks to those that reveal the mechanism behind a skeletonized portion of the dial.