When wristwatches became all the rage in the early 20th century, it was not considered proper etiquette for a woman to check the time during a social engagement. But a secret watch, disguised as a bracelet, kept the dial hidden underneath a jeweled cover so a lady could remain discreet.

Today, discretion has given way to jaw-dropping designs laden with sparkling gems as secret watches go to extremes when it comes to blurring the boundary between jewelry and watches. The six-figure prices, typically only given upon request, are also kept under wraps. At the pinnacle of the discipline are the world’s premier jewelry houses, such as Cartier and Van Cleef & Arpels.

Van Cleef & Arpels recently revived its iconic 1930s-era Ludo bracelet as a stunning secret watch with a gold bracelet composed of geometric hexagonal links underscoring its Deco roots. You can take your pick of three different combinations of hard stones and sparkling gems: chrysoprase paired with blue sapphires, emeralds, and diamonds; coral with rubies, mother-of-pearl, and diamonds; and lapis lazuli with pink and blue sapphires, mother-of-pearl, and diamonds. The modern Ludo is also a shape-shifter—transforming from watch to pendant to clip in the blink of an eye.

Swiss Maison Piaget, renowned for record-breaking feats in ultrathin mechanical watches, also takes the secret watch genre to remarkable heights. The Natural Harmony watch appears to be a spectacular diamond and emerald bracelet, until you slide open the cover to reveal a radiant black opal dial. Piaget has a decadeslong history of using stones, including phenomenal black opals, for watch dials, a specialty in its own right. The one-of-a-kind white gold cuff is set with 171 diamonds totaling almost 25 carats and 114 emeralds weighing in at more than 12 carats.

Designers in Chopard’s Haute Joaillerie workshop in Geneva channeled the romance of the Far East to create the spectacular Lotus secret watch. Because of their unusual life cycle, lotus flowers are considered sacred in many Eastern cultures, where they symbolize rebirth and enlightenment.

Chopard’s master jewelers sculpted the jeweled, articulated petals of the bloom in lightweight titanium set with pink and blue sapphires, amethysts, tsavorites, garnets, and emeralds. With a push of a hidden button, the blossom opens to reveal a jeweled dial with yellow-orange sapphires and yellow and white diamonds. The multistrand 18-karat white gold bracelet is evocative of the floating plants’ viny roots adorned with tourmalines, amethysts, and tsavorites.

The latest Médor secret watch from Hermès is an over-the-top high-jewelry version decked out in a cloak of almost 23 carats of dazzling white diamonds. The Médor collection takes its inspiration from the Parisian house’s original studded dog collars. Médor is the French version of “Fido.” The first Médor secret watch emerged in 1993 with a watch dial hidden beneath the main “Clous de Paris” pyramid-shaped stud. The design has remained a mainstay at Hermès.

The new Médor Haute Joaillerie proves that understatement can be overrated. The watch’s sole three-dimensional pyramid glistens with 196 white diamonds concealing the mother-of-pearl dial. Meticulously set with 601 diamonds, the bracelet evokes the brand’s signature gradated herringbone pattern, and requires more than 610 hours to create.