A rare imprint and plate number block of six 1893 Columbian $4 stamps realised $550,000 at Robert A Siegel in New York on November 6, up 83% on a $300,000 high estimate.
Only three examples of a $4 plate block have ever been recorded.
The stamps were issued in 1893 to mark the World's Fair Exposition in Chicago - the first commemorative stamps to be released by the US government.
They feature scenes from the life of Christopher Columbus.
The $4 issue depicts Queen Isabella alongside Columbus - making it the first US postage stamp to feature a woman.
Just 26,350 examples were ever printed.
This example is taken from the bottom left of the plate.
The condition is excellent, with only light hinging on the top three stamps and a small number of minor surface scuffs.
The bottom three stamps are mint not hinged.
A $3 plate block sold for $260,000, up 30% on a $200,000 high estimate.
Only three $3 plate blocks are known to exist and none have been auctioned in the last 25 years.
This example is taken from the top position and is thought to be unique.
Just 27,650 of the $3 stamps, which show Columbus describing his third voyage, were ever printed.
Four of the stamps are mint and unhinged, and there have been some minor repairs to perforations.
We have a range of rare stamps available.
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