This is an item that you will have to find in order to complete a Wolverine week 3 challenge, where your mission will be "Find a sentry head on the dirty docks".
To find the head you will have to go to the G4 grid reference to find the giant Sentinel body on the ground.
What you have to do is climb up his body until you reach the head, interact with him to complete the challenge. Which will unlock the Sentinel Head's back glow, which has some markings on the back, probably from a fight with the Sentinel at some point.
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