Wikipedia
Buff leather is a strong, soft preparation of bull's or elk's hide, which was worn under mail armor in the middle ages to deaden the effect of a blow. As armor fell into disuse, buff coats, which would turn a broadsword cut, and even a pistol ball, were often worn in lieu of complete steel, either with or without a cuirass and gorget of metal. Modern buff leather, of which soldiers' cross belts and other accoutrements are frequently made, is for the most part made of common buckskin.
Usage examples of "buff leather".
Kathryn said pensively, hands on her Sam Browne and fingers tapping the buff leather.
Stainless steel stabbed through buff leather and flesh and bone, and he barely managed to withdraw it in time as the guardsman wrenched his arm back with a scream.
He was dressed with rustic simplicity in buff leather breeches and a short leather coat with a handsome plaid wool scarf wrapped around his neck.
His buff leather jerkin was slick with it, and he could feel it stiffening already in the fine hairs on the backs of his hands, clotting in his hair and beard where it had spattered.