Barracks Office Key is a miscellaneous Story Item in Act Three.
A small iron key.
Properties
Miscellaneous Items
Rarity: Story Item
Weight: 0.01 kg / 0.02 lb
Price: 1 gp 
UID
S_KEY_LOW_BarracksMetalDoorUUID
aada9a18-5e3f-4356-a409-a3f6d9f06c5b