It should be standard on the right security shoulder.
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You can buy the shoulder, but you cannot use the knife, it is purely for looks. They are part of the Security armour set. You unlock it at General rank and can see it at Brigadier. There's Left and Right. Left is mirrored and has no knife, and costs 70,000 credits. Right has the knife, and costs 270,000, presumably for being incredibly awesome.
it is on the chest piece of grenedier
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