Sir Arthur Conan Doyle never wrote a story in which Sherlock, a fictional character, worked on the real-life Jack the Ripper case. However, Dr. Joseph Bell, the real-life inspiration for Holmes, was consulted by Scotland Yard on the case.
The film is one of the few to show a revolver which Dr. John H. Watson (Donald Houston) could plausibly have used as his service revolver in the British Army, namely, an Enfield Mk II in .476 caliber (used by Sherlock Holmes (John Neville) to shoot the vase in the sitting room). It was first fielded in 1880, the year Watson was famously wounded at the Battle of Maiwand.
The closing Baker Street sequence alluded to Sir Arthur Conan Doyle's 1892 short story "The Adventure of the Blue Carbuncle".
Frank Finlay also played Inspector Lestrade in Murder by Decree (1979), another film that pits Sherlock Holmes against Jack the Ripper. Anthony Quayle appeared in both films as well, in different roles.
Robert Stephens was the original choice to play Sherlock Holmes. He later played the role in The Private Life of Sherlock Holmes (1970).