The General Flipped at Dawn - S3-E1
Visible crew/equipment: After Hawkeye disobeys General Steele's orders, when it cuts to the preliminary hearing in the mess tent, the chalk T-mark can be seen on the floor under the bench at the chopper pilot's feet, where he will stand in a moment.
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 ★