Continuity mistake: While Trapper and Hawkeye are lying on their cots, one by one everyone joins them in the Swamp, and in Trapper's closeups the "USA sterilized" that's printed on his pillow is upside down, but in the wideshots his pillow's flipped over with the print right-side up.
Visible crew/equipment: Before the meeting in Henry's office starts, when Margaret and Frank take their seats, under Frank's chair we can see the chalk T-mark on the floor behind him.
Continuity mistake: When in the Swamp, and they show Hawkeye numerous times, the door to the stove is open, then closed, then open, etc.
Revealing mistake: There is a lag between the interior lights going out and the exterior stage lights going on.
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 ★