Republic P-47 Thunderbolt (Fighter-bomber)

[Louis]

Calibrating the armament of P-47 Thunderbolt. Look at the guy below. What the hell is he wearing in your eyes?

 

[mTk]

I would think it has something to do with the MG alignment?
No idea how that would work though.

 

[Gunner]

I tried looking up more info on the device but couldn't find anything other than it's used to align the guns.