PARIS — In the online forums where watch nerds and collectors gather to discuss the industry and grumble about brand marketing and rocketing prices, the Chanel J12 is often referred to as a fashion watch.

You know, one of those timepieces more at home in the scented, accessorized and couture-wearing world of its Parisian headquarters than the rarefied air of top-end Swiss horology.

But fans and many critics agree that the ceramic all-black or all-white unisex timepiece has helped shape the watch design landscape since its introduction in 2000.

“The J12 was the first revolution of the watch world in the 21st century,” said Arnaud Chastaingt, who became director of Chanel’s Watchmaking Creation Studio in 2013. “It broke classic codes. Which brand today doesn’t have a black watch in its collection?”

Last year, he redesigned the watch, from narrowing the bezel to tweaking the typeface. “It was important to me to go in a feminine way,” the Frenchman said during an interview in late February at Chanel’s Place Vendôme boutique. “This watch is full of masculine codes. But my obsession is to work on a feminine execution.”

It also was equipped with Calibre 12.1, an automatic movement with a five-year warranty produced by Kenissi, the Swiss manufacturer that Chanel has co-owned with Rolex and Tudor since 2018.

The J12 is the financial engine of Chanel’s watchmaking division, and the collection is to total 45 models by the end of the year. “It’s the vast part of our business, not far from two-thirds,” said Nicolas Beau, the brand’s international business development watch and fine jewelry director.

Chanel, privately owned by Alain and Gérard Wertheimer, does not break down annual revenues by category. But analysts at the Swiss private bank Vontobel estimated Chanel’s 2019 watch sales at 140 million Swiss francs ($145.2 million), or slightly more than 1 percent of the group’s expected 2019 sales total. (Chanel has not released last year’s sales yet, but, in 2018, they were $11.1 billion.)

From the First

Chanel has not been in watches for a long time, especially in comparison with some well-known Swiss brands. It entered the market in 1987 with Première, a cocktail watch created by Jacques Hélleu, who at that point had been the house’s artistic director for nearly three decades.

In the early 1990s, Mr. Hélleu decided he wanted a sports watch and, after seven years of development, the J12 debuted. (He named the timepiece for the 12-meter J-class racing yachts of the 1930s, which were enjoying a revival at the time.)

The watch was round, in 38 millimeters or 33 millimeters, with masculine proportions, and made of what the brand called “high-tech ceramic,” a glossy, lightweight material that resists fading and is almost as hard as diamond. Ceramic had been used in watchmaking before (chiefly by Rado), but rarely — and Chanel’s decision to use the kind of complex material applied to space shuttle heat shields was considered ambitious.

Traditional watch circles, however, were not impressed. Elizabeth Doerr, co-owner and editor in chief of the online watch magazine Quill & Pad, has been covering the industry for almost 30 years. “In 2000, the arrival of the J12 barely registered with the specialized watch press,” she wrote in an email. “But a short couple of years later, we had begun to sit up and take notice.

“Chanel seemed to have proven that it was taking itself and what it was doing in watches seriously.”

Critics viewed the 2019 reinvention as subtle. And Mr. Chastaingt himself said he had worked “like a surgeon rather than a designer” to change about 70 percent of the parts. Among the advances: a sapphire case back, instead of the original steel, to resist scratching.

This year, Mr. Chastaingt — whose Chanel watch designs include the Boy.Friend, in 2015, and the Monsieur, Chanel’s first watch for men, in 2016 — has created a number of new iterations to mark the J12’s 20th anniversary.

Most will debut later in the year, but two were introduced in February: the X-Ray, a 12-piece numbered edition with a case, dial and — for the first time in high-end watchmaking — bracelet of transparent sapphire crystal; and the Paradoxe, which fuses black and white ceramic in a single case. “Her whole life, she’s worn a black or a white dress, and I wanted to take that dress off,” Mr. Chastaingt said. “She’s old enough today that she can do what she wants.”

The Focus

During the 2000s, Chanel embraced haute horlogerie, setting up an atelier in the Swiss watchmaking town of La Chaux-de-Fonds and building partnerships with Audemars Piguet and the high-end movement specialists Renaud et Papi (which has since been absorbed into Audemars Piguet). Now, Mr. Beau said, Chanel’s watches are entirely made in Switzerland.

And in recent years it focused on additions like the J12 High Jewelry collection: watches set with a sparkling array of precious stones.

But, Mr. Beau said, he now has to plan the division’s future strategy, especially concerning the use of Kenissi movements, with greater care.

“We have to have a 10-year plan, so we are forcing Arnaud to think 10 years ahead,” he said. “When you are in haute horlogerie, you create movements in very small batches, and make them by hand. If there is a problem, the watchmakers can solve it. Each watch is almost a prototype.

“But when you are producing movements in thousands,” he continued, “you cannot afford to have a watchmaker changing every detail.”

Although he has designed the form of a number of Chanel calibres, or movements, Mr. Chastaingt confessed he has little interest in mechanics. “A watch is an identity vector,” he said. “I start with a story and think about a woman, the style and the signature I want to have on her wrist — I don’t start by dreaming of a calibre.

“I’m very proud that the J12 is equipped with this amazing calibre, but I’m not obsessed about the movement,” he said.

The Anniversary

After 20 years and about 400 different executions in a range of sizes and with both mechanical and quartz movements, J12’s legacy is finally becoming clear: It is a unisex watch that was far ahead of its time.

“Today, many luxury fashion brands create high-end watches, but Chanel paved the way,” said Rachel Garrahan, British Vogue’s jewelry and watch director. “The J12 is one of the most imitated designs in the market. The fact that it was marketed as unisex was also groundbreaking in an industry that continues today to have rigid notions about gender.”

Mr. Chastaingt said he knew the J12 was perceived as primarily for women — and, indeed, the Brigitte Lacombe photographs for the redesign’s campaign featured nine female stars and a lone man (the Hong Kong singer and actor William Chan). He also said that he had no ambition to create more overtly masculine versions, like the black ceramic and aluminum Superleggera models of 15 years ago.

“The size of the watch always allowed women to have something feminine but with masculine attributes,” Mr. Beau said. “That is very Chanel — using masculine attributes in fashion, such as tweed or jersey.”

Yet questions of gender soon will be irrelevant anyway, both men added. “The new generation is less concerned about watches for men, watches for women,” Mr. Chastaingt said.

It will be far more important, Mr. Beau said, for all luxury watches to be mechanical — even though consumers won’t care much about the actual mechanics of their watches.

“Our vision is that the less you need a watch, the more it will become an object of pleasure, so the movement will become more and more part of the soul of the watch,” he said, noting that Chanel is working on a mechanical calibre that will fit into small J12 cases. Such watches now are quartz.

Because of its fashion roots, some traditionalists may never be convinced that Chanel deserves a place at watchmaking’s top table, but others disagree.

“I firmly believe the J12 has become a superstar in the watch world, even if it was a slow burn and not a ‘Big Bang’ type of entrée,” said Ms. Doerr of Quill and Pad, referring to the clamor surrounding Hublot’s Big Bang introduction in 2005.

And Jack Forster, editor in chief of the online watch platform Hodinkee, said, “Today, I think it remains as fresh as ever, because the kind of penetrating design intelligence necessary to produce it is so rare.”

Mr. Beau is sure of Chanel’s place. “We are not a traditional watch brand,” he said. “But the J12 is a watch.”