Visible crew/equipment: At the start, when Colonel Potter walks into post-op to tell Margaret and Hawkeye about the fresh eggs, just as Hawkeye stands up the boom mic can be seen at the top of the screen, before the camera adjusts to the proper height.
Visible crew/equipment: In the kitchen, as Klinger and Winchester banter back and forth, the shadow of the boom mic can be seen in the upper right corner of the shot.
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 ★