
Love Story - S1-E14
Visible crew/equipment: After Radar tells Margaret that she's needed in the post-op ward Frank sneaks toward Margaret's tent, and when it cuts to Margaret walking into post-op, at the start of the shot we can see the two actors' curved chalk foot marks on the floor.

Visible crew/equipment: When General Barker opens the doors to Henry's office and finds Radar sitting behind the desk, we can see Barker's curved chalk foot marks on the floor beside the desk, where the actor will stand in a moment.
Henry, Please Come Home - S1-E9
Visible crew/equipment: After Reveille has blown, Radar comes in, and gets items thrown at him. As the door closes, there's a reflection of the studio lighting on the glass.
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 ★