Jean Ross is depicted as enjoying the Sally Bowles character, even carrying a copy of Isherwood's 1937 novella everywhere. Ross actually disliked the character and being associated with her.
At about 0:57 into the film, Jean finishes a song and stubs out her cigarette in the ashtray. The cigarette is clearly filter-tipped; however, filter cigarettes did not reach the market until around 1952.
Upon arrival at Berlin station, the loudspeaker announces a train to "Eisenhüttenstadt", which was at this time named Fürstenberg/Oder, later Stalinstadt (1950) and eventually changed to Eisenhüttenstadt (1961).
Landauer mispronounces Adolf Hitler's name. As a native German speaker just learning English, he wouldn't have made such a mistake.