NEW YORK (NYT NEWS SERVICE ).- Steve McQueen piloted it in the movie “Bullitt,” and for the next 50 years it was mostly a ghost. Now it’s heading to auction, and the speedy dark-green 1968 Ford Mustang fastback is expected to break records when it crosses the block next week at a Mecum event in Florida.

Bravely, its owner is offering the rusty, dented, largely unrestored car “without reserve,” which means it will sell to the highest bidder — however low that bid is.

The seller, Sean Kiernan, a Tennessee horse farm owner, says he is not worried that the bid will be too low. He figures the price could approach $5 million. Certainly, he adds, the car will sell for more than the $3,500 his father, Bob, paid for it in 1974.

It took only 10 minutes of screen time — the length of Hollywood’s most acclaimed movie car chase — for the Mustang (official color: Highland Green) to achieve immortality. McQueen himself raced it through the streets of San Francisco in pursuit of ill-fated evildoers in a black 1968 Dodge Charger.

As its cinematic legend has grown over the years, it has become arguably the most iconic Mustang ever, out of more than 10 million sold since the model’s debut in 1964. But what happened to the one true Bullitt Mustang has been, until fairly recently, one of the great automotive mysteries.

McQueen, who died of lung cancer in 1980, apparently owned it briefly, through his Solar Productions. In 1971, the company got rid of it and a sister model. Then it began its journey into obscurity, even as McQueen kept trying to find the car for his vast collection.

He wanted the so-called hero car, not the second model used for interior and other static shots. But he couldn’t quite catch up with each successive owner. His best chance probably came when its second owner sold it to the Kiernans via a classified ad in a 1974 issue of Road & Track magazine.

The ad read: “1968 ‘Bullett’ MUSTANG driven by McQueen in the movie … Can be documented. Best offer.” The ad (typo and all) included a phone number in New Jersey.

McQueen tracked down Bob Kiernan in 1977 and wrote him: “I would like to appeal to you to get back my ’68 Mustang. I would like very much to keep it in the family, in its original condition as it was used in the film, rather than have it restored; which is simply personal with me.”

Sean Kiernan still has the letter, to which his father did not respond.

So the Mustang, still with its handling and horsepower enhancements added for movie duty, lived on as a daily commuter for the Kiernan family until it succumbed to clutch issues in 1980. It has been barn-bound most of the time since then.

Its whereabouts finally started to leak out a couple of years ago, causing heart palpitations among the handful of outsiders in the know. An employee of Hagerty, the classic-car insurer, was called in to inspect and authenticate it, as was a Ford expert.

The expert, Kevin Marti, said he gasped when he saw it: “Oh, my God, it’s real!”

He said he had been called multiple times over the years to investigate other “Bullitt look-alikes.” Someone found the second Mustang in a junkyard in Mexico a few years ago; while still valuable, Marti noted, it does not have the same provenance or cachet as Kiernan’s hero car.

“Ninety-eight percent of the original car is there,” he told Hagerty. “It’s an incredible artifact.”

The question for Kiernan then became: What to do with it?

A movie was discussed, but funding proved problematic. Ford, which has introduced two “Bullitt Mustang” homage models since 2008, was interested in showing it alongside its newer versions. Hagerty suggested placing it on the National Historic Vehicle Register.

Ultimately, Kiernan decided to sell it. That decision wasn’t easy, he acknowledged, nor was his choice of the auction house to handle such a landmark sale. He selected Mecum, a less prestigious auctioneer perhaps than the big names in the business such as RM Sotheby’s and Gooding.

RM sold a 1968 Ford GT40 used by McQueen as a camera car in the 1971 movie “LeMans” for $11 million in 2012. But RM also infamously botched the sale of a $20 million Porsche last year. Gooding and others specialize in full classics and European supercars.

But cars from America’s so-called muscle car era are right in Mecum’s wheelhouse. Mecum also set a record in 2019 for sales of Mustang-based cars when it notched a $2.2 million sale for a 1967 Shelby GT500 Super Snake.

The auction, Jan. 10, will be televised on NBCSN, which is likely to result in even greater interest.

Kiernan’s decision to offer the car in a no-reserve sale is highly unusual; historically significant cars typically might be offered with a reserve, or a minimum price the seller might accept. If the bidding did not meet the reserve price, the owner would retain the car.

Kiernan decided, “I don’t want to sell the car twice.”

A Hagerty spokesman, Jonathan Klinger, said Kiernan probably had no need to worry.

“There is still a very active portion of collector-car culture that thinks of Steve McQueen as the ultimate car guy,” he said. “The King of Cool.”

Mecum’s founder and president, Dana Mecum, estimates the Bullitt Mustang will sell for at least $3 million. McKeel Hagerty, the insurer’s chief executive, predicted something closer to $4 million.

McQueen-owned or -driven cars have a history of fetching premiums. A 1967 Ferrari 275 GTB by Scaglietti that he owned sold for $10.175 million in 2014. In 2015, Mecum sold McQueen’s 1976 Porsche 930 Turbo for $1.95 million — a good five times the value of a typical Porsche Turbo.

Kiernan said he would be happy to see the Bullitt find a new home, even though it has been in his family for 45 years.

“It has to go,” he said. “I only have a two-car garage.”

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