Nobody knows when Oscar Waldan’s 100th birthday will take place. In fact, it may have passed. Such uncertainty about time is ironic for a man whom some regard as an unsung master American watchmaker of the 20th century.

He was born in Dobczyce, Poland, and any record of his birth date is among the things he lost during internment in two Nazi concentration camps: Buchenwald in Germany and Theresienstadt in present-day Czech Republic.

But Waldan International, the boutique luxury watch company he founded in 1979, is poised to make a comeback, driven by its new chief executive: his 23-year-old son, Andrew Waldan. Watch industry insiders, who regard Waldan watches as something of a secret, are applauding its return.

The watches, which are made in Switzerland and cost $8,000 to $36,000, are known for the high number of complications — which are everything a watch does in addition to telling time, like displaying the date or moon phase — and relatively modest price, said Daryn Schnipper, Sotheby’s senior vice president and chairman of its international watch division. “They’re very highly jeweled, they’re well finished and they are attractive, and their price point is very reasonable,” she said.

As a child in Poland, Oscar remembers disassembling and putting back together his father’s pocket watch. In the camps, he apprenticed with a watchmaker named Manek, a fellow inmate. Keeping the guards’ watches running afforded Oscar favorable treatment and aided in his survival.

After the war, he arrived in New York on a refugee ship in 1946 and got work as a designer for Tissot (he was a creator of the Tissot Navigator in 1953, he said) and later for the Holzer Watch Company, Tiffany & Company and Van Cleefs & Arpels.

He founded Waldan International in 1979 because, Oscar said, “I wanted to make something under my own name.” The company not only produced its own line, but also made branded timepieces for clients like the Museum of Modern Art.

But about 15 years ago, because of Oscar’s advancing age and unsold inventory, the company stopped making watches. “The hiatus set us into a point where we had become completely irrelevant in the market,” Andrew said. “That’s when I realized we had to rebrand, and give the company a new face and a new presence.”

Later this year, Waldan will present its first collection designed by the younger Waldan. Though Waldan watches are theoretically unisex, the designs will have a more masculine presence and incorporate modern materials, like carbon fiber, but retain the vintage Swiss movements that the company is known for using.

“Everything I learned was from my father,” Andrew said as the two sat in the private dining room of a senior living facility in Edgewater, N.J. The younger man was neatly turned out in a preppy cardigan and shirt. Despite his youth, he exudes an aggressive American confidence with a well-tailored, European politesse.

“He sat me down when I was 10 and put a pen in my hand, and wanted to see exactly what artistic talent I had,” he said.

Oscar, who wore a crisp gray jacket and baby blue sweater, added in a frail voice: “I taught him to believe in something and fight for it. It’s the best thing you can do.” Strapped to his wrist was a favorite gold watch of his own design: a square-shaped quartz model called the 0511.

Oscar married late in life, and had his only child when he was in his 70s. “When Andrew came along, I took him with me to work,” said Teresita Waldan-Moreno, 51, who came to the United States from the Philippines in 1990, and was married to Oscar for 11 years, during which time she worked in the family business.

“Andrew had his crib and playpen in the office, so he started from two months being in the watch business,” added Ms. Waldan-Moreno, who has since remarried and works as a marketing executive at Wempe, a longtime Waldan retailer.

Waldan International’s return was announced during Art Basel Miami Beach in 2013 with a flashy party at the Raleigh Hotel. The company received modest publicity for giving watches to celebrities like the tennis star Jimmy Connors and the rapper and actor LL Cool J. But it was an ad in WristWatch Magazine, a trade publication, that caught the eye of the influential Rhode Island watch dealer Ray Grenon, who owns Grenon’s of Newport.

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“I met Oscar 20 years ago; he had a name in the business and was kind of a best-kept secret,” Mr. Grenon said. “He just did a heck of a watch for the money, and they’re beautifully made. Then he kind of disappeared, and I heard nothing of Waldan for a good 15 years.”

Mr. Grenon said he called after seeing the ad, and was delighted to renew his business relationship with Andrew. “He’s great, and he’s young, which I appreciate in this business, where generally the average age is deceased,” Mr. Genon said, joking. “He still has a few little things to learn, but he’s got his dad there to teach him.”

As for Oscar himself, pride in his achievements and son are balanced by the enormous weight of his own life experience.

“My past is hanging over me,” he said, sitting in a wheelchair as sun streamed through the window. “No matter how successful I became, I still remember the concentration camps. I will never forget.”

But he can still make visitors smile with an unexpected memory. Asked for a recollection of Manek, his tutor of more than 70 years ago, Mr. Waldan waved his hand. “He was a very unimaginative person,” Mr. Waldan said. “The only thing he knew was watches.”