For the Good of the Outfit - S2-E4
Revealing mistake: Frank is shaving; when he bends down to pick up the envelope containing shrapnel fragments, the foam on his face and ear suddenly all dries up. The shot must have needed a lot of takes. (00:07:20)
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 ★