In an early scene while the titles are being shown, Joan Thursday, Mrs. Armstrong, Gloria Deeks and Haldane are shown on the top deck of a bus. When Mrs. Haldane gets up to ring the bell, a man is shown reading the Oxford Mail. The headline says "Woman Strangled" and underneath it says "Oxford housewife willing opened door to killer." which doesn't make sense. The camera then cuts to a close-up of the paper and it has been corrected to "Oxford housewife willingly opened door to killer."
When Endeavour looks in Joey Lisk's address book he sees an entry for Luisa Armstrong.
The address given is 42 Clind Close; but when he goes to visit Luisa the number on her front door is No. 9.
Morse references the biblical book "Revelations." There is no such thing. Correct is "Revelation," a matter Morse would certainly know.
A sign for Hire Purchase in Burridges department store window says "Happiness by Installments". The double l is North American spelling and would not be seen in 60's Britain.
The Remembrance Day poppies worn by various characters have green plastic stalks. In the early-to-mid 1960s the stalks of the poppies were bare metal wire.
DS Jakes remarks that women nowadays (i.e., in 1966) prefer what he calls "pantyhose" to silk stockings. "Pantyhose" was not a widespread term in 1966; people more commonly just said "tights".
Mr. Quinbury lost a leg flying as an RAF Spitfire pilot during WWII yet he is wearing an RAF tie with the half-wing Navigator brevet.