LONDON — A good white T-shirt is often the making of any male star on the big and small screen.

There’s James Dean in “Rebel Without a Cause,” Brad Pitt in “Fight Club,” Marlon Brando in “A Streetcar Named Desire,” Sean Penn in “At Close Range,” and now the latest addition to that list is Jeremy Allen White, whose T-shirt in the series “The Bear” has morphed into its own pop-culture entity. 

His T-shirt is the white 215 style from German brand Merz b. Schwanen that weighs 8.6 ounces, retails at 79.90 euros and is made on a special loopwheeled machine from the 20th century.

The brand dates all the way back to 1911, but for most of its time it was under dust until husband-and-wife duo Gitta and Peter Plotnicki discovered a Merz b. Schwanen Henley shirt at a flea market in 2010.

“It was so special. The fabric was absolutely amazing and the details were so nicely made because it didn’t have any side seams, which is what really caught our eye,” said Gitta on a Zoom call.

The couple, who at the time were freelance designers, ventured out to find out how the shirt was made as there was no obvious label, apart from a care label that carried the brand’s name.

Gitta and Peter traced the machine to a picturesque village in the Swabian Alps.

“They [the village people) were like, ‘oh look, freaks from Berlin coming and trying to get a 100-year-old machine running again.’ But there was a guy who did his own production and worked with fabrics; he helped us dust them off and get them running again,” explained Gitta.

They eventually found a few retired people in the village who knew how to work the machines and provided them with patterns for making the Henley shirts.

Gitta admitted that it was a challenge at first because it was different to modern patternmaking where side seams are included.

In a eureka moment, Peter told his wife that they should completely go for it and start a brand.

“You’re completely crazy; we have a little child,” Gitta replied at the time to her husband.

Without an investor, the couple decided to sell their apartment and put all their money into the company, which at the time still didn’t have a name.

They had pondered over calling it Plotnicki, but felt it wasn’t “sexy to sell.” They reverted back to the stitched label that read Merz b. Schwanen.

Merz is a family name in Germany and the b. Schwanen means “at the swan,” which all translates to “Merz at the swan.”

The Plotnickis were tracked by descendants of Balthasar Merz, the founder of the company, through word of mouth from the village.

The couple asked their permission to take it over after it had stopped production in 2008.

“All the Merz descendants came together, even the eldest and an uncle, they all gave us their signature that we’re allowed to carry the name. It was really emotional,” said Gitta.

With a brand under their wings, the couple and business owners booked a little booth at the Bread and Butter trade show, which was acquired by Zalando in 2015.

Merz b. Schwanen was met with positive feedback at the fair and is now stocked at more than 100 stores worldwide, including in Australia, France, Italy, Japan, Ukraine to the U.S. and U.K.

It was at retailer Self Edge’s New York store that “The Bear” costume designer Courtney Wheeler discovered the brand when she asked for “a really good T-shirt” and the sales assistant suggested Merz b. Schwanen.

Wheeler bought all of the store’s Merz b. Schwanen stock, as well as T-shirts from other brands, but Gitta and Peter had no clue that their white T-shirts would catapult into a TV item phenomenon. 

“We found out like everybody else did, on Instagram and Reddit. It was such an amazing surprise. You can’t even dream of it because it’s so positively insane what happened and we can’t express our gratitude enough,” said Gitta.

In a coincidence, the first person to place an order on the Merz b. Schwanen website that launched in 2016 was a New Yorker, like White’s character Carmen “Carmy” Berzatto in the hit Hulu TV show.

According to Gitta, the perfect T-shirt should “underline your personality, but it doesn’t stand out.” The details she looks out for are the triangle inserts under the armpits which have been inspired by the flea market Henley shirt; the baseball stitching, and the height of the seam from the hem.

Merz b. Schwanen’s offerings go beyond the perfect on-screen white T-shirt, however, with categories that have expanded into knitwear, sneakers, dresses and pants.

“The Bear” T-shirt remains a bestseller, with only one size available on the website right now, but before its debut on White, items from Merz b. Schwanen had already made their way onto the silver screen.

Gitta and Parker produced ‘50s style crewneck T-shirts in white for the 2017 film “Wonder Wheel,” starring Justin Timberlake and Kate Winslet; Jason Momoa wore a charcoal Henley in “Aquaman,” and Claes Bang wore the brand in “The Last Vermeer.”