A circular-shaped Alexandria, District of Columbia 5c Black postmaster provisional was the joint-top lot on the first day of the Frelinghuysen Collection stamp auction in New York on March 28.
Valued at $75,000-100,000, the US provisional sold for $550,000, an increase of 450% on the high-end estimate.
Described as "very fine" by the auctioneer, the 1846-1847 specimen is one of just six known examples.
Three of the six are Type I. The other three, including this one, are Type II.
As with all of the other recorded stamps of its type, this specimen was cut in a distinctive circular shape. It is uncancelled, and lacking its adhesive gum.
Billed as "one of the great rarities of United States philately," it had last appeared on the market at the Ferrary sale of 1922.
It is signed on the back by Leonidas W Durbin: "L. W. Durbin/July 1879". Durbin was the Philadelphia stamp dealer who bought this stamp from the man who discovered it in July 1879.
Also selling for $550,000, 83.3% above its $300,000 estimate, was an Annapolis 5c Carmine Red on White postmaster provisional cover.
As we anticipated, an 1846 Millbury postmaster provisional cover also performed well above estimate. Last seen in the 1940s, and featuring a red "Paid" cancel, it achieved $400,000, 166.6% above its $150,000 high valuation.
One of just 16 known examples of the stamp, the cover builds upon the fine used example with light red circular cancel which sold for $21,976 in Canada last week.