unknown inner cap

This is really bizarre but I believe this to be an inner lining cap used in Vietnam
A vet I think once told me that this a trench light
I said what is and he s said used to dig trenches in the night or used to go through trenches and destroy the enemy
Their are alligator claps in the pictures. I suspect to use a battery
I also suspect if you hadtto use a light it would be better .
But I don't know I have not seen one xactly like this one...I know for a fact its authentic. Any insight on this type of helmet wouldbe nice