On Nov. 10, 2022, members of the watchmaking world filled the plush 1,300-seat Théâtre du Leman in Geneva for the Grand Prix d’Horlogerie de Genève, the industry’s premier annual awards event.

Most of the nominees, dressed in everything from black tie to business casual, were present. But Stephen McDonnell, who designed the LM Sequential EVO chronograph in collaboration with the Swiss independent brand MB&F, knew that his watch was nominated in the chronograph category and had decided he was too nervous to attend.

He hid in his home workshop in Belfast, Northern Ireland, that night, watching the livestream through his fingers. “I didn’t tell anyone, not even Emma, my wife, that the ceremony was taking place,” he said. The chronograph winner was announced; it wasn’t the Sequential.

But then, Jean-Christophe Babin, chief executive at Bulgari — which had taken the top prize in 2021 — opened the final envelope of the evening, and declared the Sequential the winner of the grand prize, the Aiguille d’Or.

As Maximilian Büsser, the founder and chief executive of MB&F, made his way to the stage and collected the trophy, Mr. McDonnell was shouting with joy — he was the first Irish watchmaker to win the top award.

Alarmed, his wife came rushing in to see what was wrong.

It took six years for the Sequential to go from concept to prize. And while Mr. McDonnell is proud of the watch, he mentioned in a recent interview that the years had taken a toll: “Everyone else sees something really cool; for me, I see years of purgatory.”

The Idea

One evening in November 2016, Mr. McDonnell was in a beachside restaurant in Dubai, in the United Arab Emirates, where Mr. Büsser lives.

The MB&F Legacy Machine Perpetual watch, Mr. McDonnell’s first design for the brand, had just won the Calendar award at the 2016 Grand Prix, and he was in town to give a talk about innovative mechanics at Dubai Watch Week, which was exhibiting the prizewinning timepieces. At that time, he had been designing mechanical watches for about six years, using the training he received at Watchmakers of Switzerland Training and Educational Program, best known as WOSTEP, in Neuchâtel, Switzerland.

Mr. Büsser had invited Mr. McDonnell to dinner because he couldn’t wait to show off the vintage Tiffany chronograph pocket watch that he had just bought. “I was so proud of it,” he recalled recently.

But Mr. McDonnell was not impressed: “I could just see all its technical faults.”

“Its precision is rubbish; all chronographs have inherent technical flaws and functionality,” he remembered telling Mr. Büsser. “As soon as you turn on the chronograph, it sucks away about 30 percent of the watch’s energy and eats away at the timekeeping ability and the stopwatch function.”

Mr. Büsser asked if he had a better idea.

“Maybe,” Mr. McDonnell replied.

“Then let’s do it,” challenged Mr. Büsser.

A chronograph is a stopwatch that can measure the passage of time during, for example, a sports competition or a chess game. The invention is attributed to Louis Moinet, a French horologist, who in 1816 created what he called a compteur de tierces (in English, counter of thirds) to time the passage of stars, planets and planetary moons. The first commercial application was created in the early 1820s, when King Louis XVIII of France commissioned one of his royal watchmakers, Nicolas Mathieu Rieussec, to develop a watch that could be used to time his racehorses.

“With a conventional chronograph, all you can do is stop, start and return to zero,” Mr. McDonnell said. “You can’t time multiple things. You can’t time multiple events that all begin at the same time. You can’t time individual laps.” His reinvented chronograph does all of those things, in part because it has two chronographs, alongside its traditional timekeeping function.

“Because there are two independent chronographs,” said Mr. Büsser, 56, “you can time two different things at once — for example, the eggs and the pasta, racecars doing laps.”

It also has what MB&F calls a “Twinverter,” a binary switch that inverts the current operation — so if you hit the switch, the chronograph that was running stops and the one that wasn’t running, starts. (It’s one of the five functions Mr. McDonnell invented for the Sequential that have been patented by MB&F with the Swiss Institut Fédéral de la Propriété Intellectuelle and the World Intellectual Property Organization, a U.N. agency.)

And, Mr. Büsser noted, the Sequential is “the first chronograph in history that doesn’t lose any precision or amplitude when you switch it on.”

Asked to explain amplitude, Mr. McDonnell pointed to the watch’s balance wheel: “You see the wheel that’s jumping around? That wheel is actually the timekeeper.” When the watch is wound, the energy that is generated keeps the wheel moving back and forth — the more movement, the better the timekeeping.

The watch, available with an orange dial or a black dial and a leather strap, sells for 168,000 Swiss francs (or the equivalent of $193,190), plus tax. MB&F has said it can make 35 to 40 Sequentials a year (it expects to make a total of 420 watches this year) and as of late last month, the model had a wait list of more than 400 would-be buyers.

Mr. Büsser noted that sales were no longer made on a first-come-first-served basis: “If you already own an MB&F piece, you get first refusal,” he said, part of an effort to reward customers who have supported the brand since it was founded in 2005, and to deter speculators who want to make a quick profit now that resale prices of MB&F timepieces often exceed their retail costs.

The Process

After traveling home from Dubai in 2016, Mr. McDonnell spent the next two years finishing projects for another client. But he had also started designing a dual chronograph movement — in his head.

“I have an ability to zone out and see things in 3-D,” Mr. McDonnell, 49, said. “I spent months designing the watch in my mind before I ever put pencil to paper.”

Until he watched the Netflix series “The Queen’s Gambit,” in which the protagonist, a chess champion, mentally projects chess pieces onto the ceiling, Mr. McDonnell had believed everyone could do that. “I mentioned it to my wife, and she said, ‘That’s mental!’”

In mid-2018, finally free of other assignments, Mr. McDonnell flew to Geneva and, at MB&F’s headquarters and factory, he formally proposed his chronograph to Mr. Büsser and the brand’s co-owner, Serge Kriknoff, who is also its head of research and development and production.

He had brought along a single freehand sketch of the watch with its various dials: two for chronograph seconds at 3 o’clock and 9 o’clock, two for chronograph minutes at 1 o’clock and 11 o’clock, and one for the time at 6 o’clock. “I was very happy with the idea,” Mr. Kriknoff said during a recent interview, “if it was possible.”

MB&F agreed to pay Mr. McDonnell for three months, beginning in May 2019, so he could do some preliminary work on the mechanics. “If it wasn’t viable, we’d walk away, no strings attached,” Mr. McDonnell said. For several weeks, the emails were almost constant between Belfast and Geneva to settle on the size and placement of the dials, essential information that Mr. Büsser and his design team needed to determine the watch’s aesthetics.

Mr. McDonnell also began a virtual construction using computer-aided design (CAD) software, building geometric maps of how the hundreds of parts — wheels, levers, springs and the “trickiest parts: vertical clutches” — would function together. “There could be a catastrophic technical issue lurking — a gremlin in the works — and possible unsolvable flaws,” he said recently.

In August 2019, Mr. McDonnell returned to Geneva with his first draft of the computer-aided design to the MB&F technical team. It included parts that didn’t exist: an oddly shaped pinion and the vertical clutches that would be needed to run both the traditional timekeeping mechanism and the chronograph (when it was switched on).

Mr. McDonnell waited for the team to pick holes. “Which they did!” he said. “It was like the Spanish Inquisition.”

But MB&F approved and, as he had with his previous project, he started work without a firm timeline. “I’ve never signed a contract with MB&F,” he said. “It’s all done on mutual trust.”

He and the team were to meet every three months or so — but Covid came along. The MB&F factory and offices closed for two months, and international travel all but stopped, so the watch’s technical and design details were thrashed out entirely by email. (Mr. McDonnell didn’t return to Geneva until Aug. 6, 2020.)

In October, he emailed a complete technical dossier on the chronograph’s movement, with an individual drawing of each of its 585 parts. Twenty percent of the parts would be produced in-house by MB&F; Mr. McDonnell would make the unconventional, untested and expensive components in his own workshop; and Mr. Kriknoff had to get the rest from the brand’s more than 40 suppliers, a process made even more difficult by pandemic-related supply-chain problems. Now that the watch is in production, all the parts are made by MB&F and its suppliers.

At this stage, the watch was still virtual. But in mid-February 2021, Mr. McDonnell began to build a prototype in steel and brass, an aesthetically muted version of the final product. “It’s brute,” he said, displaying it to a visitor recently, “there’s no color on the dials, no pretty finishes that wouldn’t add anything to the mechanics.”

(In April, following Mr. McDonnell’s gamme de montage, or assembly plan, MB&F’s watchmakers started to assemble a prototype of their own, focusing on aesthetics like the finishing, the color of the wheels and bridges, and the style and color of the hands and dials.)

Mr. McDonnell also realized the clutches — components vital to ensuring timekeeping accuracy — weren’t working. But unlike the conventional time-losing chronographs he had complained about, his chronograph was gaining time.

“I ran it for 24 hours, and it gained about 20 minutes,” he recalled. “I thought I was losing my mind!” It took five months to recalibrate the friction that was causing the problem, and replace the brass wheels with lighter titanium versions, but by mid-July, the clutches worked.

A prototype of the movement was fully functional by mid-November and, for the next six months, MB&F technicians stress-tested the watch. Mr. Kriknoff invested more than 250,000 Swiss francs in a VARIOcouple machine, a device that makes extremely accurate measurements of the microforces and microtorques that can affect a watch’s timekeeping. Mr. Kriknoff also strapped on the watch for his favorite stress check — known in the office as the “Serge test” — which involves cycling to work over Geneva’s cobblestones. It passed.

The Introduction

In January 2022, the LM Sequential EVO finally went into production. Each timepiece is built from start to finish by one of four master watchmakers. (The brand has nine in all.) Initially, it took as long as three weeks to assemble; now, it takes less than two.

Emmanuel Maître, one of those watchmakers, has been with the company for 10 years. “For a watchmaker,” he wrote in an email, “assembling a complex piece like the Sequential is always more challenging and therefore rewarding than a simple movement. I also find the Sequential movement incredibly beautiful — and assembling something that’s not only challenging but beautiful is a bonus!”

On May 30, 2022, the day before the Sequential was introduced to the watch media in Geneva, Mr. McDonnell received the press kit, full of glossy photos of the watch. He was overwhelmed. “I’d never seen what it looked like finished,” he said. “There it was in all its visual glory. I cried my eyes out for an hour!”

The next day, he attended the presentation. “I found it terrifying,” he recalled.

Not the crowd, the watch. “I glanced at it, then made them take it away. It was too emotionally charged.”

By the next morning, MB&F said, it had 122 orders and affiliated retailers around the world had begun receiving hundreds of inquiries. One was placed by Dr. Nishant Patel, a heart surgeon who lives in Jupiter, Fla. He has been collecting watches since 2017 and bought his first MB&F watch, Mr. McDonnell’s Legacy Machine Perpetual, in 2021. “Like most people, I started with the most popular name brands like Rolex, Omega,” he said.

“My interest in watches stems from my profession,” Dr. Patel, 41, explained. “Heart surgery requires speed, efficiency and the utmost precision; it’s very akin to the mechanical aspects of watchmaking.” Over time, he discovered more technically complicated timepieces — primarily the creations of independent watchmakers — and was hooked.

Dr. Patel’s Sequential, the black version with the white strap, arrived in Florida on May 13. He rushed to his dealer, Provident Jewelry in Jupiter, to pick it up.

“It’s a masterpiece!” he wrote in an email that day. “It’s a stunning piece of art, juxtaposed with ingenious engineering.” Although the watch’s 44-millimeter dimension is fairly large in comparison with other contemporary watch designs, the doctor said he found the Sequential comfortable and light on his wrist and that he likes what he called its “sporty” appearance and “Miami Beach vibe.”

“I spend most of my days in the operating room,” he said, “but as soon as I’m out of work, I wear the Sequential on trips to the beach with my kids. I’ve even gone swimming with it on.” (MB&F says the timepiece is water-resistant up to 80 meters, or about 260 feet.)

It’s not his only stopwatch. “I have a couple of other chronographs by Rolex and Omega, but I never switch them on,” he said. “They’re great watches but have almost zero functionality. They just time one thing over one period of time.” In contrast, he uses the Sequential when he is grilling dinner: “One for the burgers, another for the corn,” he said with a laugh.

“I absolutely adore wearing it. I stare at the back of the watch and get lost in the maze of the mechanics. Every time I wear it, I switch on the chronograph to see the magic of it all.”