Here's how to get the Secret Diamond Camo in  Call of Duty: Black Ops 2.

First you need to unlock the Gold camouflage for all the weapons in a specific class (Assault Rifles, SMGs Sniper Rifles, etc.) in Multiplayer mode to unlock the Diamond camouflage for all weapons in that class. For example, get the Gold camouflage for all Specials (Assault Shield, Ballistic Knife, Combat Knife, and Crossbow) to unlock the Diamond camouflage for all Special weapons.

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