Many fashion trends are a matter of inches. This one is a matter of cinches.

The fireman jacket, a variation on the three- or four-pocket chore coat that features weighty metal clasps in place of buttons, has emerged as a curious, clangy spring jacket trend.

Adrien Brody, pre-Oscar win, wore a fireman jacket in British GQ. Supreme, the streetwear agenda-setters, offers one in glossy cowhide for close to $1,000. Instagram-marketed brands like Ronning in Britain target early adopters with waist-length clasp jackets for about third of that price. Vintage dealers, reporting increased interest, offer them for even less.

When worn, fireman jackets are part fidget toy, part ASMR doodad. Those metal clasps lock together with a pleasing click, like a seatbelt on a roller coaster. As the owner of a vintage version from the nearly forgotten Italian label Energie (purchased for around $175 at 194 Local, a New York vintage shop), I can tell you that those closures are pleasing to idly toggle as you, say, contemplate how to write a spring jacket story.

(As is perhaps obvious, it’s those shiny clasps that lend the coat its name. Authentic firefighter’s jackets feature metal clips that are easier to fasten than buttons or zippers while wearing gloves.)

Still, fireman coats have been around well before the term ASMR was in use. A 1979 article in the St. Joseph Gazette in Missouri includes a photo of a man in a $150 metal-clasped “fireman’s jacket” from the defunct men’s label Hunter Haig. “Firemen take risks,” the accompanying article read. “That’s why they need a coat that can take the roughest treatment in the worst weather.”

(Vintage dealers today will tell you to never buy a genuine used fireman’s jacket, which may have, if not carcinogens soaked into it, then at least a smoky odor.)

Through the 1990s, jackets with gleaming clasps were common at mainstream-leaning labels: Liz Claiborne, Isaac Mizrahi and Structure, all of which are, if not shuttered, then shells of their former selves. It was Ralph Lauren, though, who was most closely associated with the style. Liam Gallagher, the Oasis frontman, was wearing a color-blocked version from the brand back in 1994. Photos of him in the blue-and-white coat still cycle around the internet.

“Ralph definitely made them way more wearable,” said Matt Roberge, a vintage seller in Vancouver, British Columbia, who currently sells a $350 denim fireman’s jacket with a corduroy collar and a $250 washed-out-to-near-pale-blue model, both from Polo, both decades old.

“I found a fireman’s jacket in a vintage store a few years ago, and I wanted to update it,” said Sigurd Bank, the founder of Mfpen, the Scandinavian label that produced the tri-clasp jacket Mr. Brody wore in British GQ. Mfpen’s version (now entirely sold out on its site) came in a washed denim fabric, with corduroy panels on the back. For the clasps, Mr. Bank used an Italian manufacturer who made closures for authentic fireman outfits.

If the fireman’s jacket is becoming popular, it’s doing so in the wake of a broader trend: the embrace of barn coats. Barbour and J. Crew have collaborated on a barn jacket, now nearly sold out. The GQs and Vogues of the world are hailing them as the coat of the moment. L.L. Bean is importing a heretofore only-in-Japan lightweight version of its 100-year-old field coat design. And designer labels like the Row and Auralee have brought the barn to the boutique with four-figure upsells.

“I had reached barn coat fatigue,” said Jalil Johnson, the writer of the fashion newsletter Consider Yourself Cultured in New York.

Mr. Johnson, instead, went searching not for a barn jacket clone, but a cousin. He took to duffle coats, the very Anglo, rope-closed wool overcoats, but he did acknowledge that fireman jackets were another contender in the barn-jacket-but-just-off-enough contest.

“It is a continuation of all these jackets we’ve seen, but it’s more interesting because of the hardware,” Mr. Johnson said.

And that, in the hairsplitting manner of micro-trends, makes it worthy to shoppers. “It goes no deeper than ‘I like these clasps,’” said Kiyana Salkeld, a product designer in New York who owns a pair of fireman coats from Brut, a French label riffing on vintage workwear.

They are, she said, similar enough to the J. Crew barn coat she’d worn for 15 years to slot effortlessly into how she already dressed. The clasps were sturdy and reassuring but not so heavy as to distract.

Said Ms. Salkeld, “It’s just nice to have a slightly different version of the same thing that you had previously.”