Among all the superlative wristwear at Cannes, one watch in particular stuck out—a gold bracelet-like piece dripping with diamonds on the wrist of A$AP Rocky.

Called the Monete Catene High Jewellery secret watch, it’s actually part of Bulgari’s ladies’ collection—though as we well know by now, this designation does little to stop sartorially adventurous men from adopting such pieces. Made of 18-karat rose gold, it features an octagonal case and a rose gold chain bracelet set with roughly four carats of precious stones. The secret sauce, however, is that the dial is hidden, but not quite in the manner of, say, a Jaeger-LeCoultre Reverso: In this case, it’s safely tucked away behind a nearly two-millennia-old coin embossed with the visage of the Roman emperor Caracalla (198-217 AD).

Daniele Venturelli

Open the hinged case cover with the emperor’s likeness, and the actual dial—mother-of-pearl with diamond-set indices and a gold handset—is revealed. Serious watch heads will also appreciate the tiny power plant contained within the case: It’s Bulgari’s Piccolissimo mechanical manufacture micro-movement, a manually-wound caliber with a 3 Hz beat rate and a 30-hour power reserve. Overall, such a watch checks numerous boxes: Horological nerds will love the mechanics, history buffs will appreciate the ancient coin, jewelry lovers will love the beautiful gold and diamonds, and those simply in search of an elegant cocktail watch will dig the complete package.

Given its Roman roots, Bulgari has long incorporated such ancient coins into its jewelry. It’s also far from the only brand to design “hidden” watches: Piaget, in particular, is famous for its watches that used unique “coins” designed by Salvador Dali to hide the dial, as well as a series of timepieces with 19th-century American twenty-dollar gold pieces forming the dial cover. And while the Jaeger-LeCoultre Reverso isn’t quite a “secret” watch to the same degree as ASAP Rocky’s Bulgari, the dial is indeed hidden behind the caseback when reversed—in this instance, to protect it from errant polo ball thwacks.

Another prime example of a secret watch comes from Bulgari itself: The high jewelry versions of its famed Serpenti sometimes hide the dial within the snake’s head. Vintage Patek cocktail watches from the mid-20th century likewise sometimes obscure the watch dial behind gem-set covers, as do pieces from Omega, Van Cleef & Arpels, Vacheron Constantin, and others. A more contemporary example is from Cartier: While its Reflection de Cartier doesn’t quite hide the dial from view, the design—which uses a mirror at one end of a bangle-like cuff to reflect the dial back to the viewer—playfully obscures the time.

“Secret watches” are a highly specific, semi-obscure timepiece category that exists at the intersection of horology and jewelry—and they’re seriously cool. A$AP Rocky knows this, making for a sartorial moment at Cannes that outshone the more typical watch spotting. If you long for your own Monette watch, you can reach out to the brand directly…though one has to wonder just how many 2,000-year-old silver denarii of Caracalla the brand has lying around.