The illustration, which was stored in a garage in London, was originally sold at a clearance sale for 150 pounds, equivalent to just under 2,000 Swedish kronor, to a collector.
The work was described as an original work by the surrealist Salvador Dalí, but since it was not considered "surrealistic enough" there was a suspicion that it could be a forgery, according to The Guardian.
The new owner contacted a renowned Dalí expert who has certified that the illustration is authentic and valued it at between 20,000 and 30,000 pounds.
"Vecchio Sultano" from 1966 is drawn with both watercolor and ink pen and was part of Salvador Dalí's project to create 500 illustrations of folk tales from the Middle East. He later abandoned the project.
The artwork will be sold by the British auction firm Cheffins in October.
