The British Guiana 1c Magenta has set a new world record for a stamp at auction, achieving $9.48m in a single lot sale at Sotheby's New York on June 18.
This equates to a return of 7.94% pa since 1980, when it sold for $935,000.
David Redden, director of special projects and worldwide chairman of Sotheby's books department, commented: "I have been with Sotheby's all my working life, but before I knew about the world's greatest works of art, before I knew about the Mona Lisa or Chartres Cathedral I knew about the British Guiana"
"For me, as a schoolboy stamp collector, it was a magical object, the very definition of rarity and value, unobtainable rarity and extraordinary value...
"I have to say I'm a little sad to see it go - when I was eight years old this was the most precious object in the entire world, and I never dreamed I would have it in my hands."
It spectacularly eclipsed the previous record, set at $2.3m for the 1855 Tresklilling Yellow in 1996.
While the 1c Magenta is far from the only one of a kind stamp in the world, it carries a mythical status, having passed through some of the world's greatest collections.