An 1898 Trans-Mississippi 8c block of four made $140,000 at Robert A Siegel in New York on November 6, up 12% on a $125,000 valuation.
The finer example of just two recorded 8c plate number and imprint blocks, it is one of the rarest items of US philately.
The Trans-Mississippi commemorative stamps were issued to mark an exposition of the same title in Omaha.
They show scenes from the old west and are highly prized among collectors.
Featuring a depiction of troops guarding a wagon train, the block is the only example taken from the top of the sheet and is imperforate horizontally.
It features the original gum, good colour and a detailed impression - with just light natural gum wrinkles and a minor horizontal crease.
A $2 Trans-Mississippi block of four sold for $80,000.
The design depicts the Eads Bridge in St Louis, Missouri - and was originially used on the admission ticket to the 1896 Republican convention where William Mckinley was nominated as the party's presidential candidate.
Very few $2 imprint blocks are known to exist, especially from the top of the plate.
It features the original gum and a strong impression.
A block of 10 $1 Trans-Mississippi stamps made $75,000 against a $54,400 estimate - up 37%.
Four corner stamps have been lightly hinged, while the remainder are mint and unhinged. Minor perforation separations have been reinforced.
We have a variety of rare stamps available.
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