This is an original WWII leather liner strap. The leather is still quite soft and supple. The buckle is blackened brass, which dates the strap's production from mid to late-1944. It features United Carr stamped blackened brass rivets. The underside of the leather is stamped with an 'H', denoting production by the Hagerstown Leather Co. 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