"Holmes" (played by Andrew Gower) mentions that his client hired him with a one-pound note from the bank of Scotland ("a fine institution despite its Jacobite sympathies.") Gower later played the Bonnie Prince, Charles Edward Stuart (failed Jacobite Leader), in the series Outlander (2014).
In the final credits, the single female characters are listed with the honorific "Ms.", i.e., Ms. Ellie Naughton. This may at first glance appear to be an anachronism, but in fact the honorific "Ms." has been attested as early as 1901. It is quite plausible that modern young women would have used such a title in the very early 20th century, though the honorific was rarely throughout most of the twentieth century. Beginning in 1961, American feminist Sheila Michaels began a successful campaign to bring "Ms." into the mainstream.
This episode takes place in 1901.
Butter tarts were common in Canadian pioneer cooking. The earliest published recipe for a butter tart is from Barrie, Ontario dating back to 1900 in the Women's Auxiliary of the Royal Victoria Hospital Cookbook.