Regency Superior has announced that the incredibly rare 1930 Romanian Airmail overprints will provide the highlight of its August 23-24 auction in Connecticut.
The sheet is regarded as the world's rarest and most valuable aviation error, containing 50 2-lei 1930 airmail stamps, two of which have inverted overprints. It is estimated at $750,000-1m.
The error was apparently caused when two stamps became detached from the sheet and were reattached upside-down with gummed paper. Returned to the stamp stock, the overprint was then added for the coronation of King Carol II and the invert occurred during the process.
A total of 826 sheets were overprinted, yet just two with inverts have ever been found. The sheet retains its original gum, mostly never hinged, with only slightly rounded corner stamps and a few toned spots affecting the condition.
It is thought the sheet was once part of King Carol's collection himself, though his stamps were never found after his widow's death in 1977.
Nothing is known for certain of the sheet's ownership prior to 1980, when it was offered at Sotheby's and bought by Herbert Klein. Current owner George Rusu, who will be on hand at the sale, bought it when Christie's offered the Klein estate in 1996.
The sale forms part of the American Philatelic Society's Stampshow.
Paul Fraser Collectibles has some of the rarest error stamps for sale.