Factual error: When the camera looks at Lt. Clark, her rank insignia is horizontal. It should set from the apex (point) of the stitching diagonally (top end toward her face).
Continuity mistake: As Charles talks to the guys in the Swamp, his right hand alternates from up at his chest to down by his side several times too quickly to be normal.
Answer: The C-42 was a military variant of the Douglas DC-2. Very few C-42's were built, so it's questionable that Potter would specifically have seen that particular model, but, given his military background, it's not entirely unreasonable that he might use the military designation even when the aircraft in question is actually a civilian DC-2.
Tailkinker ★