The Orson Welles-directed 1941 classic starred Welles as a newspaper magnate and Cotton as a reporter. It was nominated for nine Oscars but eventually only won the best original screenplay honours for writers Welles and Herman J Mankiewicz.
Introduced in 1932, the No 5 was the most popular of all Underwood typewriters, and was used by millions throughout the first half of the 20th century.
The clamour for Kane memorabilia has produced some amazing auction prices:
* In 1982, Steven Spielberg bought a “Rosebud” sled on auction for $60500 - one of three balsa sleds used in the film’s final moments.
* Welles’s Oscar for best original screenplay was auctioned for $861542 in 2011.
* Mankiewicz’s Oscar was sold at least twice: in 1999 and again in 2012 for $588455.
* Mankiewicz’s personal copy of the script for Citizen Kane was auctioned at Christie’s for $231 000.