Brandon Stamp Auctions has discovered a Jessica Ennis stamp from the London 2012 Olympics with an error of vignette.
The stamp, produced to commemorate Ennis' win in the Heptathlon, shows the athlete at the Istanbul IAAF World Athletics Series, rather than at the landmark event in London as intended.
Discovered in a pane of 24 stamps at a post office in the Midlands, UK, the stamp is described by the auction house as a "major error which is sure to become a future all-time classic". It is being offered for £475 ($774) on a first come, first served basis.
Error stamps - those produced with varying faults - are some of the most valuable in philately, due to their rarity and unusual nature. Perhaps the most famous is the Inverted Jenny, a stamp to which seasoned collectors need no introduction.
Olympic stamps are also a popular collecting category. In June 2013, David Feldman held an auction dedicated to Olympic postage, with the top lot a collection spanning 1896-1974 that sold for $32,821.
Coins from the 2012 Olympics are also becoming collectible, with over £10m in 50 pence coins removed from circulation since their issue by collectors. However, it will take some time before these are worth significantly more than face value.
Paul Fraser Collectibles has a magnificent selection of stamps for sale.