The film takes place in 1900.
When the issue of "The Strand" containing Watson's account of "The Adventure of the Engineer's Thumb" arrives at Baker Street, Holmes comments that it is "appropriately accompanied with inaccurate and melodramatic illustrations." This an in-joke, as neither Edward Woodward nor John Hillerman reflect the sleuths as depicted in Sidney Paget's artwork accompanying the tale.
Dr. Watson's revolver is a Webley RIC (Royal Irish Constabulary) Second Pattern, a more realistic choice by the producers than many, since the piece at least has the virtue of having been produced prior to Watson's army service, which began in 1879. Since officers purchased their own sidearms at that time, a penniless army surgeon picking one up second-hand before shipping out to India rings true.
Peter Jeffrey (Mycroft Holmes) previously played Sherlock Holmes in The Best House in London (1969).
Final film of Honora Burke.