The pass was lost because it was not stored with others given other reporters such as German photojournalist Gerda Taro, the partner of war photographer Robert Capa, Maria Jose Turrion, the assistant head of Spain's Salamanca-based civil war archives told AFP.
Dated April 16th, 1937 the media accreditation for the author of "The Little Prince" was issued by the bureau in charge of propaganda for the losing Republican side in Spain's civil war.
All journalists who worked in Republican territory were required to register with the department.
Antoine de Saint-Exupery's press pass. Photo: AFP
Saint-Exupery was aged 36 at the time and he listed himself in the pass he filled out as being an aviator and "clerk" in what appears to be a mistaken translation into Spanish of "ecrivain", the French world for writer.
Policarpo Sanchez, a 52-year-old lawyer and amateur historian, found the press pass among other documents on June 30th in a small village in the central province of Toledo while researching civil war cinema.
"It has extraordinary value. His press pass provides us with precious information regarding his stay in Madrid," Sanchez told AFP.
Saint-Exupery had listed his address in the Spanish capital as the Hotel Florida, where many writers who came to Spain to cover the war such as Ernest Hemingway and Martha Gellhorn stayed.
The conflict pitted soldiers loyal to an elected Socialist-led government known as Republicans against rebel Nationalist troops who rose up under General Francisco Franco in his military uprising that ultimately toppled the government.
It was one of the first conflicts to be extensively covered by press around the world, especially by intellectuals who sympathised with the Republican side.
Saint-Exupery, a pioneering pilot of his era, covered the war in 1936 from Barcelona in northeastern Spain for French newspaper L'Intransigeant and then in 1937 for Paris-Soir.
He disappeared while flying over the Mediterranean in 1944, shortly after the publication of the fairy-tale-like novella "The Little Prince". His body was never found.