Last year, shoe designer Stuart Weitzman anonymously bought a 19th-century stamp for $9.5 million. Then, he slipped it into his back pocket and headed home.

“I figured the best way was not to use an armored truck. That would call attention — my goodness, an armored truck pulling out from Sotheby’s could give some hooligans something to think about,” he says.

Weitzman remained anonymous until today, when his 1856 British Guiana One-Cent Magenta goes on display at the Smithsonian National Postal Museum.

Many visitors to the museum will wonder what’s so special about this little rectangle of paper, says chief philately curator Daniel Piazza.

“It’s OK visually, but it’s nothing special,” he says. “It has a few words on it, and a little picture of a ship, but it’s been pretty heavily cancelled.”

Even Weitzman’s wife was underwhelmed by the stamp.

“When I showed it to her, she said, ‘What are you walking around with that for? It’s all beat up. It looks like it was used. It’s not even American,’ ” he recalls.

In addition to holding the record for the most expensive single stamp ever sold, the stamp is special because it’s one of a kind.

The South American colony of British Guiana (now Guyana) existed from 1831 to 1966. In 1856, it ran out of stamps from England, so the colony enlisted a newspaper publisher to print stamps locally.

As far as anyone knows, all of those stamps — the one-cent magentas — were tossed away with the newspapers and envelopes they were affixed to. Except for one, which was saved by a Scottish boy living in British Guiana in 1873. The budding philatelist discovered the One-Cent Magenta on his uncle’s old mail and sold it to a collector for six shillings, the equivalent of $1.44.

The stamp’s price skyrocketed from there. American textile magnate Arthur Hind bought it for $35,500 in 1922, probably outbidding King George V, who wanted it for the Royal Philatelic Society’s collection. Chemical fortune heir John du Pont bought it for $935,000 in 1980. He was later convicted for murdering Olympic wrestler Dave Schultz, and died in prison in 2010. His estate put the stamp up for auction last year.

The stamp’s checkered past is part of its mystique, Piazza says.

“We live in a celebrity culture, and this is a stamp that has had a string of celebrity owners who have been almost as intriguing or maybe even more intriguing than the stamp itself,” Piazza says.

The stamp’s newest owner is now a part of that history.

Though he doesn’t think of himself as a philatelist, Weitzman did collect stamps when he was a boy, he says.

“In my international stamp album there was a place for the One-Cent Magenta British Guiana stamp. Of course, no one ever expected to fill that hole. It was there to remind us how unique and valuable a little piece of paper can be,” he says.

That’s why, when the stamp came up for auction, Weitzman decided to try to get it.

“I thought, ‘Oh my gosh, am I really going to have an opportunity to complete my album?’ That sort of drove me more than the stamp alone, remembering my childhood of stamp collecting and that empty spot on the page.”

Soon, Weitzman will release a series of purple shoes, inspired by the stamp.

“I asked my accountant if, because I have been inspired by the color of this stamp, if he thought I could take the stamp as a business expense. He laughed and said, ‘No, not unless you want to go to jail.’ ”

Smithsonian National Postal Museum, 2 Massachusetts Ave. NE; Thu. through 2017, free.

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