From 1972 to 1977, the Swiss watchmaker Piaget produced a limited series of white and yellow gold wristwatches that epitomized the brand’s reputation as an emblem of the jet set.

Iterations of the Black Tie design featured dials made of ornamental stones such as tiger’s-eye and onyx framed by three rows of textured grooves known as gadroons, and chic, cushion-shape cases measuring 45 millimeters by 43 millimeters (1.8 inches by 1.7 inches), large enough to accommodate the bulky Beta 21 quartz movements. So distinct was the collection’s style, the brand said, that Andy Warhol purchased a yellow gold model with an anthracite gray galvanic dial in 1973.

In 2014, Piaget reintroduced the model, now known as the Black Tie Vintage, incorporating mechanical movements and hard stone dials like lapis lazuli. But it could not compare with what the watchmaker unveiled in June: the one-of-a-kind Terrae Black Tie Vintage. Presented in Florence, Italy, at an event celebrating the brand’s new Metamorphia high jewelry collection, the one-off will retail for at least $339,000, according to a spokeswoman.

With its mottled brown dial of petrified wood surrounded by three rows, nearly six carats, of baguette-cut Colombian emeralds, the piece bore the unmistakable stamp of Stéphanie Sivrière, the brand’s creative director of jewelry and watches. For the last 21 of her 47 years, she has honed a design style at Piaget that emphasizes minimalist dials and textured details, such as her signature use of gadroons.

When designing the Terrae, “the only thing I had to be aware of was not to go wrong,” Ms. Sivrière said through a translator on a recent video call from Piaget’s headquarters in Plan-les-Ouates, an industrial suburb of Geneva. “The design is so beloved that if you go wrong, there are consequences.”

That statement could easily serve as her job description. Ms. Sivrière’s role requires a delicate balancing act — respecting the legacy of a nearly 150-year-old brand while simultaneously reinventing it for contemporary watch buyers.

“The key is never to design for a specific audience, gender or nationality,” she wrote in a follow-up email. “It has to feel authentic and then the magic appears.”

Ms. Sivrière referred to two new timepieces with vivid green dials in Piaget’s Polo collection, a perpetual calendar and a Polo Date Field watch, the modern-day successors of a model that the brand introduced in 1979, when the luxury sport watch category was still coming into its own.

“In both cases, we paid homage to this icon in a versatile and vibrant way with the electric green dial, and by adding the gadroons on the dial to bridge this piece with the past,” she wrote. “It’s a play on signatures that ended up working, but if you force it too much, it doesn’t always work.”

For example, Ms. Sivrière said she would never add a complication, such as a tourbillon, to the dial of the Black Tie Vintage. “You cannot put something too strong on this watch,” she said. “The dial has to stay minimal and pure.”

Yet she took the opposite approach to the new Polo Emperador, scheduled to debut in December. The watch features a skeletonized, ultrathin diamond-set tourbillon movement with 5.94 carats of emeralds on the bezel.

The details of the piece required Ms. Sivrière to work closely with Guillaume Chautru, Piaget’s head of gemology, as well as the movement designers at the Piaget factory in La Côte-aux-Fées, the village in the Swiss canton of Neuchâtel where the brand was founded in 1874. They all had to ensure that the nine trapezoid-cut emeralds decorating the oscillating weight did not disrupt the watch’s ability to keep accurate time.

“One of the great things at Piaget is we have 50 percent jewelry and 50 percent watches and I like to mix the design,” Ms. Sivrière said. “There are a lot of things you can gain by mixing expertises.”

She would know. Ms. Sivrière has spent the past seven years perfecting that combination.

Born in Paris in 1975, Ms. Sivrière grew up between the mountain resorts of Megève and Chamonix, in southeastern France. She was drawn to jewelry at a young age, after meeting a friend of her father’s who worked in the diamond trade. “I was mesmerized by the beauty and reflection of this stone,” she wrote.

Ms. Sivrière enrolled at a jewelry and gold smithing school in Paris, since renamed the Haute École de Joaillerie, where she studied various jewelry-making crafts. After graduation, she worked freelance for a jewelry company on Place Vendôme in Paris. Then, in 2002, she joined Piaget as a jewelry designer, attracted, she said, by the opportunity to help the brand, known as a traditional watchmaker, strengthen its jewelry business.

“It was a different time for the brand and the industry; fine jewelry wasn’t as big as today,” she wrote.

In 2011, Ms. Sivrière was named director of jewelry creations, and in 2016, she began overseeing watches, reflecting Piaget’s newfound interest in ensuring that its watch and jewelry designs were in harmony.

“When I was asked to work on watches, it was a challenge because they had two different vocabularies,” she said. “Today, it makes perfect sense. I can play with both.”

On her wrist, Ms. Sivrière regularly wears what many watch lovers would consider the purest distillation of the brand’s watchmaking expertise, the Altiplano Ultimate Automatic, “the essence of Piaget’s artistry in a watch,” she wrote.

The model runs on the brand’s ultrathin 910P automatic movement, which is 4.3 millimeters thick. Thinness has been an in-house specialty since 1957, when Piaget introduced its mechanical hand wound 9P caliber.

At a thickness of just 2 millimeters, the movement kick-started an industry arms race of sorts over slimness. (Since July 2022, the Richard Mille RM UP-01, a collaboration between the watchmaker and Ferrari, has held the crown at 1.75 millimeters thick.)

But above all, Piaget’s more flamboyant history as a watchmaker for “the Diana Rosses and the dandies” is most resonant with contemporary watch lovers, Brynn Wallner, founder of Dimepiece, an editorial platform centered on watches and pop culture, said by phone from New York.

“The people are ready for the Piaget revival,” Ms. Wallner wrote in a follow-up text message, referring to myriad comments she received on an Instagram post that she wrote in March from the Watches and Wonders Geneva trade fair, where Piaget had rolled out a well-received collection of timepieces flashing back to its heyday in the 1960s and ’70s.

Reflecting on the era, and Piaget’s starring role, Ms. Sivrière couldn’t deny its hold on her. “It’s a never-ending source of inspiration,” she wrote. “There are a lot of gems from the other decades, but the boldness of these years keeps astonishing me.”