The page of text in the prop book "Witch, Warlock and Werewolf" is the exact words related by George and Janet's inner voices. However, the same paragraph of text is printed multiple times down the page.
The monster's fangs visibly wobble and move when it closes its mouth as it dies, clearly revealing them as a prosthetic.
Janet (Gloria Talbott) is shown running through the outdoor night barefoot. But when she checks her shoes in her room, they are muddy.
The script mixes up traditional "horror-film folklore" about how to deal with specific monsters. Jekyll is described as a werewolf, affected by the moon, despite having used science and drugs to effect his transformation rather than being bit by another werewolf. Later, his dead body is said to have been staked through the heart to stop it rising to search for blood, which is more like a vampire than a werewolf.
Although the film is set in the early 20th century, at one point in the background you can see a 1956 Chevy and a 1956 Ford pass by.
Toward the end of the film, Dr. Lomas in his "werewolf" state, happens upon the cottage of a of a young woman. Inside, there is a telephone and an Edison phonograph, neither of which would be present in a rural British dwelling in the early 20th century. The young lady and the telephone operator both speak with American accents. And the cottage's dweller is wearing anything but period attire for the year 1900.
During an early conversation Mrs Merchant states "Mind you, I'm not a local woman. I come from near Liverpool". However, she has neither a Liverpool, Lancashire or North Welsh accent, all of which would be very distinctive. Instead she speaks in a slight lowland Scottish "Received Standard English" accent consistent with a servant living in the Edinburgh location of the original story of "Dr Jekyll and Mr Hyde", despite the film supposedly being set in England.
Boom mic visible numerous times throughout the movie. Once at 14 minutes into the movie, another at 37 minutes, 40 minutes, and 47 minutes. Plus a few more times.