This is an original WWII leather liner strap. The leather has conformed to the shape of a helmet's brim, but is still quite soft and supple. The buckle is blackened brass, which dates the strap's production from mid to late-1944. It also features United Carr stamped blackened brass rivets. This would be an ideal strap for a high-pressure helmet liner with either green painted steel or blackened brass A-washers.
WWII Leather Liner Strap With Black Brass Buckle