Where to use the counting room vault key in DMZ in Modern Warfare 4

In Modern Warfare 4’s DMZ mode, the counting room vault key unlocks a door inside the Heavenly Luck casino in Cheongun Village. The key is awarded for completing the “Operation Silent Ledger” story mission, and the room contains valuable loot.

From the main entrance, turn right and follow the corridor through a security room to reach the locked door. Entering from the less guarded rear brings you onto the casino floor; cross to the southern side and head towards the main entrance hall. The room is on the floor above the Aston Martin Dreadnought and contains two safes, cash and other containers.