The gray-bearded man in the red shirt and wide-brimmed Amish hat wades into the crowd outside the Gold & Silver Pawn Shop, squinting into the noon-hour light.
Suddenly, the fans are upon him. They know their quarry on a first-name basis.
"Hi, Mark," a woman calls out. "Can we get a shot with you? My boyfriend's daughter, she just loves you."
Another stranger touches his shoulder.
"Mark, we're huge fans," says a goateed man, adding breezily, "We just got married last night."
"Well, after 35 years, I heartily recommend it," says Mark Hall-Patton, who had run an errand at the shop.
For 10 minutes, cameras whir in the parking lot on Las Vegas Boulevard; people whisper in English, Spanish and Italian, their gaze shining as brightly upon the 59-year-old museum administrator as opening-night klieg lights.
They all want a moment with one of America's unlikeliest celebrities. Since 2009, Hall-Patton has played a cameo role on "Pawn Stars," the History Channel's reality show whose quirky off-the-cuff bargaining scenes between opportunistic sellers and jaded buyers quickly made it one of cable TV's most popular programs. Now dubbed into 32 languages, the series has brought Hall-Patton international fame.
On camera, Hall-Patton is the learned authenticator in oversize square glasses who can tell the guy from Tuscaloosa, Ala., whether that Civil War musket his grandmother kept in the attic since the Great Depression is the real deal or a knockoff.
"Mark is the only rock-star museum curator I know," says "Pawn Stars" creator Rick Harrison, holding a cigarette in his office at the shop. "The guy knows so much stuff; he must have a Xerox machine inside his eyeballs. I've got a nickname for him: the Beard of Knowledge."
Hall-Patton is a voracious reader with 20,000 history books spread around his house. Through his work at various U.S. museums, he's explored Native American collections and items that span the nation's 238-year history. He also has studied U.S. utopias and fraternal societies, guns, printing, postcards and bridges.
"When it comes to history, I'm an omnivore," he says. "I'm all over the place."
Those things he doesn't know, he researches.
Richard Kunst, a Roman Catholic priest from Minnesota with arguably the nation's largest collection of papal artifacts, speaks often with Hall-Patton.
"The fact he seeks me out shows he does his homework," Kunst said. "He wants to get to the source of things."
Over five years, Hall-Patton has appeared in one-third of the series' 300 or so shows. He's praised by fans as an aesthetic purist who refuses to discuss an item's rank value, choosing to concentrate on its specific provenance and place in history.
Although he realizes "Pawn Stars" is entertainment, he says his reputation is at stake with every on-air proclamation.
"I do my darnedest to be as accurate as possible, because I'm representing myself," he says. "Whether I'm trying to determine whether something is real or not, or whether it was used this way or that, it's important to be right."
Among his fans, the museologist is best known for the agrarian hats he began wearing two decades ago - Amish originals purchased from the Pennsylvania hill country. Then there's the flowing beard that ripples and jiggles as he talks, and that baritone that plumbs deep below his diaphragm to deliver his words.
Hall-Patton sightings are a daily occurrence.
Fans stop him on the street and wave from passing cars. Women want to touch his beard. Children tug at his coat. He's been told he's the most popular TV character among the inmates at a Walla Walla, Wash., prison. Once, a hulking Mongol biker approached him in a crowded casino, making Hall-Patton flinch, before leaning down to say, "Hey, man, I like the show."
The show's main characters - Richard "The Old Man" Harrison, son Rick, grandson Corey and goofy pal Austin "Chumlee" Russell - guard their privacy against their crush of followers: They rarely appear in the pawnshop's public area, conducting business and taping the show in the back.
As an educator, Hall-Patton sees the spotlight as helping bring his heightened appreciation of historical artifacts into millions of American homes each week.
He's director of the little-known Clark County Museum, where despite no advertising budget, annual attendance has soared nearly 70 percent since 2012 - last year it reached 42,000. It is mostly because of Hall-Patton that visitors drive to the city's far southern reaches, as he says, "far away from the white noise of the Strip."
He also runs the city history museum in Searchlight and the Howard W. Cannon Aviation Museum at McCarran International Airport. He's already cultivating the next generation of museum-goers, handing children baseball-card-like mementos with his picture and museum contacts. But he can't be everywhere.
So many fans griped when Hall-Patton wasn't at the Clark County Museum that officials ordered a life-size cardboard likeness of the Beard of Knowledge - Amish hat and all - that stands beaming in its lobby.
Hall-Patton honed his storytelling style as a child in Santa Ana, Calif. From age 8, he created museum displays at his home, explaining old books and paintings to his younger brother and sister. Years later, he studied museum administration and began his career at the Bowers Museum in Orange County, eventually running the Anaheim Museum and Orange Community Historical Society.
In 1993, while working in San Luis Obispo, Calif., he was lured to Las Vegas. He immediately grasped the task ahead: "People don't usually come to Vegas to go to a museum. I'm not sure what they come here for," he joked. "Apparently, it's something else."
He never auditioned for "Pawn Stars"; the producers came to him after someone recommended him. One day at his office, he received a phone call asking whether he would go on camera and discuss the value of a West Point uniform.
He suggested they get an antiques dealer, not a historian, but the caller insisted. After the pilot episode's filming, Hall-Patton wondered, "Who on earth is going to watch this?"
Plenty of people, as it turned out. He returned to discuss such little-known objects as a set of Soviet intercontinental ballistic missile launch keys, a 17th century Dutch coin scale and the ID card from an attorney general in the Truman administration.
Depending on the shooting schedule, when the producers call with something to authenticate, he'll have as long as a month or just a few hours.
His fastest work came with a Civil War-era LeMat revolver. He'd seen enough firearms from the period to know it was genuine.
"With any object, I ask the same questions I would if it was brought into my museums: Is this thing real? And how do I know that?"
He says he's been wrong only once - about a 1930s British guard's uniform. After his research, Hall-Patton decided the pants were copies but the coat and bearskin hat were authentic. A viewer who knew the items later informed him the cap had been doctored.
"The guy was right," Hall-Patton said.
Once, when he was asked to look at letters involved in the kidnapping of aviator Charles Lindbergh's baby, they were so compelling that he called a West Coast museum that houses documents about Lindbergh to see whether any had been stolen. None had been; the letters turned out to be genuine.
Despite such adventures, he knows his fame comes at a cost: He can't lose his temper in public and has caught Internet impostors with fake Facebook pages.
His wife, Colleen, a sociologist at the University of Nevada, Las Vegas, specializing in women's studies, wrote a paper on his newfound status for an Australian journal on celebrity. She said the two were embracing at an airport after a long absence when someone tapped her husband on the shoulder.
"And I thought, 'Really? You couldn't wait 30 seconds?'"
Still, Hall-Patton stays humble.
"I've seen the Beatles; I know what real celebrity is. I'm just a bloody museum director."