British actor Robert Montgomery (IX) is listed on the opening credits of the American version as "R. Montgomery" so as not to confuse audiences with better known and very popular USA actor Robert Montgomery (I). 2nd billed Lilli Palmer is given starring billing as Lili [sic] Palmer, followed by Banks, Malo and Montgomery. No other cast members are mentioned, not even Romilly Lunge, billed 3rd in the original UK version, but apparently ignored by the USA distributors who were unfamiliar with his name.
The USA version (Chamber of Horrors) runs approximately ten minutes shorter than the original UK version (The Door with Seven Locks). The Kino Lorber DVD restoration is the USA version.
The credits of the USA version say "Produced by Edgar Wallace" (who died in 1932); prolific John Argyle was the actual producer.
This was British producer John Argyle's second Edgar Wallace adaptation after his highly successful "Dark Eyes of London" (1939) (U.S.: "The Human Monster") with Bela Lugosi.
This British production was picked up by Monogram and released (as "Chamber of Horrors") as part of a pre-packaged double feature with the Boris Karloff feature, "The Ape" (1940).