The film they are watching in the theater in the opening scene is the James Cagney film "G Men". "G Man" is a formerly popular slang term meaning "Government Man" which applied to generally to federal agents, most commonly FBI agents.
At the end when nightclub owner Bernie Cole picks his teeth with a toothpick, he places it back in the toothpick dispenser.
Chief Inspector Japp speaks of the blueprints of the submarine being stolen from the U.S. Admiralty. Now although the United does have what it refers to as Admiralty Law, the term Admiralty at that time referred to the military department that oversaw and ruled over the British Royal Navy from 1707 until 1964. There were departments of Admiralty elsewhere, especially in the Empire, but not strictly in the United States, which had a Navy Department. This more Japp just using a more familiar term to describe the workings of a foreign government department.
Mention is made of the birth of the Dionne Quintuplets. This occurred in Callander, Ontario, on Monday the 28th of May, 1934. Now mention was made previously of Bonnie and Clyde being still at large. Both were killed in Gibsland, Louisiana on Wednesday the 23rd day of May by six officers, including Texas Ranger Frank Hamer in a hail of gunfire by ambush. This could be consistent with the sequence of events.