An 1875 special printing $6 ultramarine newspaper stamp has sold for $75,000 at Robert A Siegel in New York, where it headlined the September 18 sale of the George A Schwenk collection.
The lot is described by Siegel as "one of the rarest stamps in US philately" and is one of only five in existence.
Around 500 were printed in the year of its release but only 14 were sold, resulting in its withdrawal nine years later in 1884.
They were issued for the 1876 Philadelphia International Exposition, the first world fair held in the United States.
The Post Office printed 24 variations in rising denominations (from 2c to $60) which display figures from classical mythology.
The US newspaper and periodical stamps were first used in 1865, allowing presses to send out bulk shipments using a single stamp.
The highly stylised and ornate designs were used to deter forgers and are considered among the finest examples of engraving in US postal history.
A complete set of colour proofs produced for the Atlanta International Cotton Exposition of 1881 made $33,000 earlier this week.
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