Rare stamp could bring millions at NYC auction

A tiny 1-cent postage stamp from a 19th century British colony in South America has held the auction record for a single stamp three times. Now it's poised to become the world's most valuable stamp again.
Sotheby's predicts the 1856 British Guiana One-Cent Magenta will sell for between USD 10 million and USD 20 million when it's offered in New York on June 17.
A former curator of stamps at the British Library compares it to buying the "Mona Lisa" of the world's most prized stamps.
The One-Cent Magenta was last on public view in 1986, and is the only major stamp absent from the British Royal Family's heirloom postage collection.

An 1855 Swedish stamp that sold for 2.3 million in 1996 currently holds the auction record for a single.