Visible crew/equipment: After Radar walks into the Swamp and gives Hawkeye and Trapper the coffee and case folders, just as Radar tells them that he was too sleepy he walks out, and the actor's chalk T-mark can be seen on the ground (although faint, it's distinguishable).
Factual error: The Logan Ramsey character tells Hawkeye and Trapper that with enough notice he could get them anything, even a B-52. The first B-52A entered service in 1954, a year after the Korean War ended.
Continuity mistake: As the boys talk to Col. Lambert, Trapper is back a bit from the table. When the angle changes, he's a lot closer.
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 ★