The scene in which Clemens receives an honorary degree from Oxford University in 1907 was the re-creation of an event that C. Aubrey Smith, who plays the Oxford chancellor, actually witnessed.
Shot in 1942, not released until 1944.
The typesetting machine (aka Paige Compositor) for which Clemens was so enthusiastic was never a profitable venture due to the need for continual adjustment. Clemens' investment was about $300,000, or about $7,000,000 in present day monies.
This film was made during World War II under the restrictions of the Motion Picture Production Code. Consequently, much of Twain's life was altered to appease censors. For example, Clemens was actually a deserter from a Confederate militia company in the area of his Hannibal, Missouri hometown in 1861. It was the basis of his story "The Short History of a Private Campaign That Failed".