Visible crew/equipment: In the overhead exterior shot of the compound, when Colonel Potter calls everyone's attention to the situation regarding "crackerjack corpsman" Sergeant Hutchinson, as the shot pans out we can see the boom and the boom mic at the top left corner of the screen. Then when Margaret calls on Hutchinson to come forward, the boom mic is moving around at the top of the screen, and it's still there when Klinger rides out on Sophie.
Visible crew/equipment: While Hawkeye's helping Klinger with the love letter to Laverne, just as Klinger says, "After all, you're only human, I was thousands of miles..." the boom mic dips into view at the top of the screen.
Visible crew/equipment: After Colonel Potter tells everyone in his office that he's been asked to address them about the possibility of making the army their career, the Swamp trio laugh, and when it cuts to Margaret telling the "clowns" to keep quiet, the shadow of the boom mic bounces around at the top, right side of the screen.
Visible crew/equipment: In the last scenes of the episode, the overhead shots showing the parade where Klinger rides in on Sophie, dressed (undressed) as Lady Godiva, you can see the boom mic in view at the top of the screen.
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 ★