An 1861 5c green Confederate States sheet of 100 will star in an auction at Robert A Siegel in New York.
The lot is valued at $30,000-40,000 ahead of a December 17-18 sale of Confederate stamps and postal history.
The lot is one half of a full sheet of 200
It's known as the Ackerman plate in reference to its most famous owner, Senator Earnest R Ackerman - who owned the full sheet of 200.
The present lot is from the left hand side of the sheet and remains in exceptional condition, with many of the stamps retaining their original gum.
The stamp was the first of a small number of official stamps issued in the south during the civil war and displays a profile of Jefferson Davis.
Siegel explains: "This is the only surviving pane of 100 of Confederate states 'number one'.
"[It is] unquestionably one of the most important items in all of United States and Confederate philately."
Other lots in the sale include a collection of 57 hand-painted cachet covers by Dorothy Knapp.
Knapp was a teacher who moonlighted as a designer for Fleetwood, a company that sold first day covers.
She also produced limited edition designs which are highly collectible today. The collection is expected to sell for $10,000-15,000.
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