In episode 4 of Manhattan, Frank Winter has a flashback while walking alone through the desert at night. He sees a dead German soldier lying on his stomach. On the back of the helmet there is a swastika (the sign of the Nazis in WW2). As far as I know, the flashbacks are set in World War 1 (since it is Frank himself, fighting in this war).
So how can the soldier have a swastika (also with an imperial eagle holding it) on his helmet?
Did I get something wrong or is this a mistake in the series?!