There's several scenes of Japanese Mitsubishi A6M2 'Zero' fighter planes strafing Chinese civilians and Nationalist soldiers in 1937-38. The Mitsubishi A6M2 Zero fighter plane would make its combat debut over Chungking, China in August 1940. Prior to that time, the Japanese were employing imperial Army Nakajima Ki-27 fighter planes with the fixed landing gear and the imperial Navy Mitsubishi A5M, also with fixed landing gear, later codenamed, "Claude", by the Allies. The Allies later codenamed the Ki-27, "Nate".
When Hogg photographs the Japanese soldiers rounding up the Chinese civilians from the first floor window overlooking the scene, many of the shots, and the black & white prints later produced by the Japanese officer are clearly taken with a telephoto lens. Hogg's range finder 35mm camera was not fitted with a telephoto lens.
In the rail yard scene the box cars are modern steel types and the ties are a modern concrete type although the movie takes place in the 1930's.
Throughout the film the city is always referred to by English as "Nanjing". In the 1930s all English-speaking people called it "Nanking".
At around 00:22 into the movie when they were at a railway yard and they were attacked by Japanese fighters, the tender of the steam locomotive has a China Railway Logo (this logo has half circle on top of a rail track profile). This logo was only adopted in 1950 and is still in use today. This movie is set around 1937.