The only known and recently discovered blueprint of a First World War British Mark 1 tank is to go under the hammer at auction.
The blueprint is a highly detailed large-scale technical plan of the tank, used in its design and construction, and is estimated to sell for between £10,000 to £20,000.
The Mk I was the world's first tracked armoured fighting vehicle and it hugely influenced the nature of modern warfare.
The tank's distinctive rhomboidal form is an icon of the First World War and is still immediately recognisable despite the passing of more than a century.
The introduction of the tank by the British in 1916 was an attempt to break the stalemate of trench warfare.
It was designed by Lieutenant Walter Gordon Wilson and William Ashbee Tritton, director of the agricultural machinery company William Foster & Company of Lincoln.
The blueprint being offered for sale at auction in February is accompanied by an equally unique patent specification for the tank which is thought could be sold for up to £10,000.
Carlisle-based Laidlaw Auctioneers and Valuers, headed by TV antique expert Paul Laidlaw, has been asked to handle the sale.
Mr Laidlaw, best known to viewers of shows like Antiques Road Trip, said no original blueprint of the tank was known to have survived.
He said when he first saw the blueprint it was "like seeing an X-ray of a mechanical leviathan and gives some insight into why these 'land ships' induced such shock and awe in the troops of 1916".