The famous movie car has been owned by the Kiernan family since 1974.global debut in Detroit, the Mustang that started a phenomenon and forever changed car culture will go up for sale by Mecum Auctions in Kissimmee, Florida. The market will decide its value (there is no reserve price) and some experts estimate it could easily fetch $4.5 million, a new sales record for a Mustang. The current record-holder is a 1967 Shelby GT500 Super Snake, which was bought for a staggering $2.2 million in 2019.
"I don't need to sell this car," Sean Kiernan, whose father, Bob Kiernan, purchased it in 1974 for $3,500 after seeing an advertisement in Road & Track magazine, told ABC News. "I am OK with any price. But I would like it to be the most valuable Mustang ever."
Kiernan and his sister will drive the rusty and unrestored Mustang on the auction block as wealthy collectors from around the globe bid on the car. The Mustang, which his parents drove everywhere -- the odometer reads 65,055 miles -- provided closure for Kiernan after his father's death in 2014.
"It was a family car and my father was the last one who drove it," he said. "This whole process has been therapeutic for me. My father will always be connected to this car."
Eric Minoff, a specialist in the motoring department at Bonhams auction house, said "plenty" of people will be willing to pay a large premium for the "Bullitt Mustang."
"It's the 'hero car' from one of the most famous car chases," he told ABC News. "It's McQueen's single most significant motor car scene outside of [the movie] 'Le Mans.'"
A selling price of $5 million is not an "unrealistic figure," according to Minoff, who has seen the Mustang GT several times.
"Because of the way it looks and what we know about -- the car produces a certain aura," he said. "It's pretty special."
Moreover, "McQueen memorabilia tend to sell for a lot of money," Minoff noted. Bonhams has auctioned off dozens of McQueen's cars, motorcycles and personal items like a credit card and sunglasses. In March at the Amelia Island Auction, Bonhams will sell two vehicles driven by the actor and former race car driver in "The Thomas Crown Affair" -- a Con-Ferr Meyers Manx Dune Buggy and a 1967 Rolls-Royce Silver Shadow.
"Steve McQueen holds a lot of weight with older collectors," Minoff added.
Sam Murtough, marketing director at Mecum Auctions, expects movie buffs, muscle car enthusiasts and Mustang devotees to compete for the vehicle.
"There's been a lot of interest from known and private collectors," he told ABC News. "It's not really a car anymore. It's a piece of American history."
David Conwill, associate editor of Hemmings Motor News, said he's not aware of any car that has "gotten this much buzz." But all the attention has its drawbacks, too.
"It's a burden to have something this valuable in your possession," he told ABC News. "I don't blame Sean for getting rid of it."
In 1994 the car's air cleaner was stolen. Over the past year, strangers have stopped by Kiernan's home in Kentucky unannounced, asking to see the car.
"It's become bigger than what I expected," Kiernan admitted. "I am an average guy with a two-car garage, not an eccentric collector."
Kevin Marti, a well-known Ford expert and president of Marti Auto Works, which archives Ford Motor Co.'s 150 million production records, was called on by Kiernan in June of 2016 to authenticate the vehicle. Marti, who can easily spot a fake Mustang, said his skepticism turned to elation when the car's aluminum VIN tag matched his electronic record. Ninety-eight percent of the Mustang is original, he noted. The fenders are still intact and the damage to the hood from filming was never repaired. Plus, the paint looks 50 years old, Marti said. The steering wheel McQueen gripped in the classic film, however, had been replaced by a prior owner.
The Mustang could not be "faked," he told ABC News.
But Kiernan cannot claim to be the sole owner of a "Bullitt Mustang." A few years ago Marti examined another Mustang that had been left to rot in a Mexican junkyard. The movie's stunt car, which many had assumed was crushed decades ago, was still alive, though a shell of its former self.
"It was missing the doors, fenders, engine, the whole drivetrain," Marti said. "Ninety-eight percent of the car was not there."
That Mustang was shipped to California and is undergoing a major restoration so it, too, can be auctioned for a hefty sum.
Kiernan said he and his family had decided it was time to give up ownership of the car after being its guardian for 45 years.
"This car is amazing ... but it needs to be in a collection with a team of people to take care of it," he said.
"The only reason to hang on to it is because of the emotional tie," he added wistfully. "I don't know my life without this car."