In the chaotic street scene where Jim is chased by an older ruffian, they pass a posted bill advertising the movie Gone with the Wind. While the movie did premiere in 1939, that particular and most famous poster did not appear until 1967, during its re-release.
Jim begins the film at the age of 13 or 14, meaning that when World War II ends he would be at least 17 or 18 years old. Actor Christian Bale (who was 12 when the film was produced) barely appears to age and is still a small boy in 1945.
In one scene in the American barracks in the POW camp, one prisoner is heard playing the tune "I Left My Love" on the harmonica. The tune is from the 1959 film The Horse Soldiers and was composed specifically for that film by songwriter Stan Jones, who also had a cameo in it.
When Jim first comes into the cabin of the derelict freighter to meet Bassy, the fried rice which Bassy is stirring contains something which looks like meat. Later shots of the pan and then the served meal show rice only.
As Jamie races after the truck filled with British citizens, the little boy standing in the back of the truck stares at him with his mouth alternately opened or closed, depending on whether the shot is from further away or close up.
When Jim steals the cork from the bottle during his Latin lesson, he sets the bottle to his right. When he leaves, after snatching his lesson book from the doctor, the bottle is to the far left of the table.
At the beginning, when Jim encounters the Japanese soldiers in the city as they are gathered for a meal, they are eating dumplings family-style as a group and using long, blunt-ended chopsticks. This would be very unusual for Japanese soldiers and would be more characteristic of Chinese soldiers. Japanese do not normally eat this way and their chopsticks would be pointed. If there is a common bowl of food, Japanese would turn their chopsticks around to transfer the food to their own bowl and then eat it with the narrow end only.
Jim could not have witnessed the atomic bomb explosion in Japan with anything approaching the detail shown in the film. The distance from the Chinese mainland to Nagasaki, at its nearest point (roughly 475 miles), is further than the distance from the Trinity test site in New Mexico to Denver, Colorado (roughly 450 miles.) The distance from mainland China to Hiroshima is even further (roughly 640 miles.) Even allowing for no terrain obstacles, the curvature of the earth at such a distance precludes anything more than a brief dim glow on the horizon.
When Jamie first approaches the crashed Zero at the costume party the rudder on the tail is straight. When his model plane disappears over the hill and he gets out and goes after it, the rudder on the Zero is all the way to the left. However in between these two shot's he's shown sitting in the wrecked aircraft playing with the controls, it's likely he's pressed the rudder pedals.
During the very last shot of Jim's suitcase floating in the river, a rope can be seen tied to the top right corner of the case, leading off the right side of the screen, keeping the suitcase from drifting out of the shot.
Early in the movie when Jamie is in bed, his mother is tucking him in and his father is standing over watching them both, holding a newspaper in his hand. Just before the scene ends, there is a brief cut showing where two scenes were poorly edited together (most noticeable when the father and his newspaper jump to the right).