Waiting on the stations platform a train with 1970s Bundesbahn-wagon (type "Silberlinge") leaves the station. The film takes place in the post-WW II Germany.
The clothes that the children wore are of modern variety, including the rubber waterproof boots in bright colors. The German boys during the 1920s are most likely to wear the Lederhosen and leather shoes as they are more durable than the fabric.
The US military general at the police station has the uniform from the 1950s onward (pleated chest pockets).
Several vehicles appearing in the film are from 1940 onward. A police car and military vehicle parked in front of the police station are Mercedes-Benz 220 (1951-1955) and Volkswagen Kübelwagen (1940-1945) respectively. Another car parked on the street is Citroën Traction Avant 11b (1953-1955). At the carnival, the cars from the 1970s are visible in the background.
The US military general at the police station mentioned "Nazi". The term "Nazi" wasn't coined until 1926 when Joseph Goebbels published a pamphlet. Previously, the organization was called NSDAP. The film took place in the early 1920s with the exact reference to 1925 at the end of the film.