Visible crew/equipment: When Klinger's at Little Chicago he asks one of the black market vendors about cameras and he points to another vendor, and when it cuts to the next shot we can see the actor's T-mark on the ground where the man walks away (his foot even moves the T-mark) and Klinger is about to stand.
Continuity mistake: When Klinger's stopped by the MPs it cuts to a close-up of the Polaroid camera and it's lying between the seats with its hand strap facing the front of the jeep, but when Klinger picks it up the camera's positioned the opposite way with its hand strap facing the back of the jeep.
Answer: Even an Army field hospital would have SOME weapons for self-defense if the enemy attacked. What's meant is that it's not a combat outfit, and therefore wouldn't have enough weapons to actually attack anyone. (It's also mentioned a few times that the Officer of the Watch is supposed to carry a pistol at all times, but Hawkeye refuses to do it when he's in charge and Colonels Blake and Potter don't enforce the rule).
Captain Defenestrator