Buff leather was worn by Continental troops during the Revolution. Buffalo, whether Asian water buffalo or American bison were pretty hard to come by on the East coast circa 1775. Yes there was an uncommon sub species of Bison found in the East at that time but I cannot imagine a leather industry based on it, especially as it was not until after the Civil War that a Pennsylvania tannery developed a practical method for tanning bison leather. Good news for makers of machinery drive belts, bad news for bison and Plains Indians. As for buff leather used before the Civil War that was most likely from ox hides, oxen being common in 18th Century America and well before that. The Old French word for ox was buffle.