Visible crew/equipment: After Hawkeye shows up in Colonel Potter's office with severe allergy symptoms, BJ and Margaret walk out with him, and when Potter says, "Time we found out what's on his mind," the shadow of the boom mic moves across the door.
Visible crew/equipment: A crew member is visible in Margaret's tent when she confronts OR nurse Helen about her drinking, approximately halfway through the episode.
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