One of the great oddities of the Third Reich arsenal, the "krummlauf" device was a cause of a great deal of confusion on the part of the Allies when examples were captured. As a mechanical concept, curving a barrel to change the path of a bullet seems to stretch credibility, but the Germans figured out how to do it. The first examples were built for test-firing high-powered anti-aircraft weapons, allowing test shots at elevated angles, and were later adapted for field use. A krummlauf-equipped assault rifle or machine gun could be used by infantry to fire over barricades or around corners without exposure, or mounted in compact ball turrets on tanks and vehicles as a point defense weapon against sappers and enemy infantry. In addition to being equipped with the distinctive prismatic sight that allowed the operator to see what he was aiming at, this model is equipped with a later adjustable gas bleed device. The barrel is marked "VG 23", with "23" on the left side of the reinforcing bracket, and "rln" (Carl Zeiss of Thuringia) just below the viewport of the prismatic sight.