Odd coincidence: on the tow truck being used for the underground radio station, above the cab is the company's phone number that includes the word "Barbarossa". "Operation Barbarossa" was the code name for the German invasion of Russia, which began on 6/22/41--just days before this film's general release.
The Maltese Falcon sits behind Fräulein Gessner's desk at Gestapo HQ. It is from the original production, The Maltese Falcon (1931), not the classic remake The Maltese Falcon (1941).
This film is an example of how quickly "B" pictures could be released in this era. The characters mention Rudolf Hess' flight to England, which was reported to the media on 5/13/41, only six weeks prior to the film's premiere. They were also under the misapprehension that Hess had defected from the Third Reich when he was really on an ill-considered mission to convince England to leave the war. The film also notes the death of a character's son in the sinking of the battleship Bismarck on 5/27/41 after the Battle of the Denmark Strait on 5/24/41.