OWLS HEAD, Maine — You never know where one of your old cars will turn up.

MBNA founder Charles Cawley learned that lesson while attending the 31st annual New England Auto Auction at the Owls Head Transportation Museum on Saturday. A noted car buff with an extensive collection of antique and classic automobiles, Cawley was pursuing the Mercedes Benzes and Rolls Royces when he spotted a familiar green 1993 Bentley.

“That’s the car I was driving when I first came to Maine, and I last saw it when I traded it in New York 15 years ago,” Cawley said. “I don’t know how it got here, but it shows you how things go around.”

Cawley recognized his old Bentley because of the custom pin-striping he had done on it. The striping runs the length of the car and is painted the colors of the flag of Ireland, home of his ancestors.

Phil Crosby of Belfast couldn’t believe his eyes either when he spotted a 1972 MGB convertible that used to belong to his son-in-law Sam Mehorter. The last time he saw it, Crosby said, the roadster was in the Frankfort garage of his friend Richard Robertson, who bought the car from Mehorter last year.

“I can’t believe it,” he said. “I hope it finds a good home.”

Billed as “one of the great summer events in New England,” the weekend of the annual auction is circled on every car lover’s calendar. Serious buyers arrive Friday to preview the cars and stay all day Saturday to take in the action.

For this year’s edition, auctioneer and museum director Charles Chiarchiaro was treated to a sun-splashed day that filled the museum grounds to overflowing. The parking lot was packed and a school bus was used to ferry visitors to the grounds from an auxiliary parking area on Route 73.

More than 400 registered bidders and nearly that many patrons attended the annual event. Serious buyers and dreamers walked side by side among the more than 200 antique and special interest automobiles from every era. They gazed at their reflections in gleaming paint jobs and looked under the hood.

“I’ve been here many, many times. I just enjoy vintage cars,” said Mark Joudrey of New Market, N.H.

Spectators were seated under open air tents and easily observed each model up for auction as it was wheeled onto an elevated stage before them. As Chiarchiaro is fond of saying, “There is nothing like the experience of driving with the family in an antique, classic or special interest automobile. Whether a Rambler or a Rolls Royce, an old automobile makes many memories.”

Chiarchiaro joked to the crowd that he drives a “Beverly Hillbilly Cadillac. There’s a mink coat and a chamber pot in the back.”

Bob Emery of Steel’s Real Rod and Custom shop in Rockport was 14 years old when he attended the museum’s first auction and bought his first car, and he has attended every auction since. He is a corporate sponsor of the museum and was happy to see the large crowd of bidders and spectators. Emery has a collection of 50 old cars.

“This is great,” he said. “I can’t wait for things to get started. I’ve got a front row seat.”

Rod Semler of Mt. Laurel, N.J., said he hoped to find a mid-1950s Ford station wagon for his father. He said his father had an old wagon, but rather than spend the money to restore it, he hoped to find him one that was already done.

“I’d like to find him one in turnkey condition,” Semler said.

The auction is often a multigenerational event. Nick Hurd of Southport had his 9-year-old grandson Grant Auber with him for good luck. Hurd said he had good luck finding what he wanted at the auction over the years.

“I’ve sold cars and I’ve bought cars. Sell them right, buy them right,” Hurd said. “Grant was 7 years old when we bought our Porsche. He held up the card and placed the winning bid.”