The barrel column in the old factory ledger uses K for Krupp, D for Damascus and S for the plain steel used on the 0-Grade shotgun barrels. The flyer introducing the O-grade listed it as being available with Damascus or fluid steel barrels, as did the 1907 Three Barrel Gun Co. catalog. By the 1908 Three Barrel Gun Co. catalog the 0-grade is said to be made with Crescent Steel Barrels.