Shoe designer Stuart Weitzman has announced himself as the new owner of the world's most valuable stamp, the British Guiana 1c Magenta.

American Weitzman ended months' of speculation on the same day the stamp went on display at the Smithsonian National Postal Museum in Washington, DC.

'What are you walking around with that for?'

The 19th century stamp sold for $9.5m at Sotheby's New York in June, demolishing the previous stamp auction record of $2.3m, set by the 1855 Treskilling Yellow in 1996.

Weitzman recounts how after making his winning bid, he took the stamp home in his back pocket.

"I figured the best way was not to use an armored truck," he told the Washington Post.

"That would call attention — my goodness, an armored truck pulling out from Sotheby's could give some hooligans something to think about."

He also details his wife's reaction to seeing the stamp for the first time.

"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."

The stamp has proved a striking investment over recent decades. The most recent sale price equates to a return of 7.9% pa since 1980, when it made $935,000.

The 1c Magenta is thought unique. And while there are other unique stamps in the world, its fascinating history ensures its record-breaking value.

It has passed through some of the world's greatest collections, including, most recently, that of John Du Pont, whose life was the subject of the 2014 film Foxcatcher.

The stamp will remain on display until November 2017.

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