Military Courier's Key
Description
Open the Military 
Lockbox inside the Hotel Lobby in Hotel Halperin.
Location
Drops from the 
Military Courier. The NPC seems to only spawn after you have completed the Rav-ages of Caustic-X side quest. Once its done, run out of the lobby, and then return, and it should begin spawning new zombies in the lobby, including the Courier.
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