In his memoirs published in a fanzine of the Britain-based Association of Comic Enthusiasts (ACE) years ago, British comics artist Basil Reynolds, who had also worked in editorial capacity in Britain's Mickey Mouse Weekly in the post-World War 2 years, recounts how he had once visited famous illustrator Fortunio Matania (1881-1963) and borrowed a b&w original of one of his illustrations ("a jousting scene") to use on a cover of MMW ("as the large opening pictıre of a Disney strip") in colors. Above scan is of the cover of no. 592 (dated Sept. 15th, 1951) of MMW, which must obviously be the cover in question.
Big thanks to John Wigmans for providing me the Reynolds memoirs...