An example of the world's first postage stamp, the Penny Black, is being offered at auction, Sotheby's said on Tuesday, with a price estimate of up to $8.25 million.
Dating from 1840, the item is "the earliest securely dated example of the first postage stamp," according to the auction house that will present it at its "Treasures" sale on Dec. 7.
The adhesive stamp, which features a profile of Queen Victoria, is attached to a document dated April 10, 1840, from the archive of British postal service reformer Robert Wallace, a Scottish politician. The Penny Black, which introduced a flat rate, was used from May 6, 1840. Before that, the recipient paid the postage cost.
"This is the first ever stamp, the precursor to all stamps, and unequivocally the most important piece of philatelic history to exist," Henry House, head of Sotheby's Treasures Sale, said in a statement.
"Though there are many hugely important stamps in collections both public and private around the world, this is the stamp that started the postage system as we know it."