As Hannay looks out the train window as Police Board the train, a "First Class" symbol appears on the window. This is in the BR "Totem" style, which did not appear until 1948 when the UK Railways were nationalized.
While in Scotland, as a guest at the ancestral home and on the heaths, Hannay, wears Cherry Red Dr Marten Airwear boots (first invented in 1960). These are first seen under a chair while he is changing in the bedroom.
At the health resort where Hannay is drugged by the Prussian agents, a concert is taking place. As the guests assemble, we see a poster advertising the concert, which gives the date as Wednesday, 13 March 1914. 13 March that year was a Friday.
When the police and Hannay search Appleton's house, they find a dummy head with false hair, beard and moustache for Appleton to impersonate Sir Walter. Appleton had already left to go to Westminster to carry out his plan, but how could he without these vital items?