A rare mid-19th century New Zealand 'bisect' is coming to auction at Spink in London on June 8.
The vertically bisected green one-shilling cover is expected to make between £8,000 and £10,000 at the sale of the Dr Robert Towers collection.
The stamp was employed on a letter from Otago, New Zealand to Edinburgh, Scotland in 1859.
Due to a lack of sixpenny stamps, a resourceful Otago postal clerk simply halved a 1855-57 one-shilling (worth 12 pence) specimen instead.
Featuring what Spink calls "very rare provisional franking", the stamp was produced in Auckland on blue paper.
Just 26 bisects are known to exist, a fact that is sure to have collectors and investors highly interested in this piece.