An apparently rare stamp used on a postal ballot in the US mid-term elections is a fake, experts have said.
Four "Inverted Jenny" stamps sold for almost $3m last year
Officials in Broward County, Florida, said they saw a famous "Inverted Jenny" stamp while reviewing postal ballots.
About 700 of the stamps were mistakenly printed in 1918 with an upside down illustration. Just 100 examples made it into the hands of the public.
But, now philatelists have examined the stamp, they have found it is a common fake of the famously rare article.
"To a trained philatelist, it's pretty obvious that it's a counterfeit," said expert Randy Shoemaker.
The give-away signs included an incorrect number of border perforations, the stamp's thickness and its colour.
"The colour, to me, was off. It looked more bluish-green than the blue of the genuine," commented Mercer Bristow of the American Philatelic Society.
The stamp was examined by experts for an hour, comparing it to an authentic "Inverted Jenny" and another fake one.
But, because of its intriguing story, the Smithsonian's National Postal Museum says it would like to display the envelope with the fake stamp.
The original stamps bear a picture of a Curtiss JN-4 plane, known as a Jenny, which was used for training pilots in World War I and later became an airmail plane.
The stamp was spotted by Broward County Commissioner John Rodstrom who said he recognised it from when he collected stamps as a child.
The official said the envelope had no return address, and the ballot was disqualified because it gave no clue as to the identity of the voter.
In October 2005, a block of four Inverted Jenny stamps sold for $2.7m (£1.52m) at auction.