A stamp described as the world’s rarest sold for $9.5 million at auction last night, setting a new record.

The auction house Sotheby’s said the “British Guiana One-Cent Black on Magenta” went to a phone bidder who chose not to be publicly identified.

The previous auction record for a single stamp was $2.2 million, set by a stamp called the “Treskilling Yellow” in 1996.

The previous owner was  John E. duPont, heir to the chemical company fortune and an avid collector. duPont, who also was a patron of amateur wrestling, paid $935,000 for it in 1980. He was later convicted of murdering a freestyle wrestler with whom he had had a falling out. He died in prison in 2010.

The price last night in New York was below Sotheby’s pre-auction estimate of $10 million to $20 million. But Sotheby’s vice-chairman David Redden said in a statement he was nonetheless “thrilled with tonight’s extraordinary, record-setting price of $9.5 million.”

He called it a “truly great moment for the world of stamp collecting. That price will be hard to beat, and likely won’t be exceeded unless the British Guiana comes up for sale” again.

The stamp is a storied one. A British schoolboy living with his family in British Guiana (now Guyana) who was a fledgling stamp collector  discovered it in 1873 while going through his late uncle’s personal letters.

It had been printed in 1856 by a newspaper publisher in the colony of British Guiana after the local post office ran out of stamps shipped from London. The postmaster was unhappy with the quality of the stamps and concerned they might be counterfeited. So he ordered postal clerks to personally initial each stamp at the time of sale to prevent fraud, according to a history offered by the Kenmore Stamp Company.

Vaughn offered the stamp to a local dealer who had no interest until Vaughn told him he would use the proceeds to make a few purchases. The dealer agreed to buy it for six shillings, the equivalent then of about $1.50.

“Now look here, my lad,” the dealer reportedly said, “I am taking a great risk in paying so much for this stamp and I hope you will appreciate my generosity.”

That was an early link in a long chain of ownership that would make the One-Cent perhaps the most famous stamp in the world.

“You’re not going to find anything rarer than this,” Allen Kane, director of the Smithsonian National Postal Museum told the AP. “It’s a stamp the world of collectors has been dying to see for a long time.” 

David Beech, longtime curator of stamps at the British Library who retired last year, has compared it to buying the “Mona Lisa” of the world’s most prized stamps, the AP said.

In 1980, DuPont bought it anonymously.

Du Pont, who was called  “the wealthiest murder defendant in the history of the United States” by prosecutors in Delaware, shot Olympic wrestler David Schultz three times at point-blank range on Jan. 26, 1996, on the grounds of du Pont’s Foxcatcher estate, where Schultz, 36, lived in a guest house with his wife and children. After the shooting, DuPont retreated to his mansion and held police sharpshooters at bay for two days before he was captured.

After hearing sometimes conflicting testimony from psychiatrists, the judge in DuPont’s trial concluded that he was  “severely mentally ill.” Court-appointed psychiatrist Steven Mechanick concluded that duPont had significant delusions, including thinking he was the Dalai Lama of the United States.

At the time, Schultz was coaching du Pont’s wrestling team in training for the summer Olympics.

At last night’s auction, according to the New York Times, “a crowd of stamp dealers and collectors filled the auction room, with a row of television cameras in the back. ‘I don’t think they’d get that coverage for a van Gogh,’ said Frank J. Buono, a stamp dealer from Binghamton, N.Y. ‘And by weight and volume and size, it’s the most valuable item in the world. Diamonds might fetch more, but they weigh more.’

You can read more about the sale here.