This may count as one of Robbins of Dudley's more bizarre designs. In that it was extensively copied by other manufacturers during the Great War, it must have been a popular design as well. There even exist some homemade examples, cobbled together from scrap brass and at least one hollow cast iron one. Another non-Robbins knife has the knuckle bow cast in aluminum integrally with the handle. The Robbins originals comprised a cast aluminum handle cast onto a steel knuckle bow and a double-edged 5' blade resulting in a weapon whose design makes it almost impossible to drop while being nearly idiot proof in action. And yes, you CAN stick it through a car door. See link below. I've made this knife from aluminum with a blade of hand-forged file steel, hardened and tempered. The blade is blackened as is the steel knuckle bow. Includes a sewn cowhide sheath.