The crime in this story is based upon a real life event, the sensational Great Train Robbery that occurred two years before this episode. In both cases £3 million were stolen from a Royal Mail train. After adjusting for inflation, the loot would be equivalent to almost $64,000,000 in 2014.
There are two references in the course of this story to "the case of the Stefanini Dowry" - presumably referring to the third episode of this series, which is indeed called "The Stefanini Dowry".
Closing credits: The characters and events depicted in this photoplay are fictitious. Any similarity to persons, living or dead, is purely coincidental.