Continuity mistake: When Hawkeye and Eddie are dancing in the Swamp, after Hawkeye sits on the hot heater Eddie knocks over the tray of glasses and the mug, but next shot the mug is back up on the table.

Revealing mistake: While Hawkeye and Eddie are in the Swamp, when Eddie knocks over the stovepipe we can see that it's actually split into two pieces for the stunt, whereas in the previous shots it's not.
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 ★