A martial variant of a John Browning designed sport gun, the 520 Trench Gun was originally developed in response to a World War I request for new fighting shotguns for the American Expeditionary Force. It made a strong impression on the evaluators but did not make it into the field before the armistice was signed. Seeing potential for the gun on the police market, Stevens kept production going to 1932, and at the outbreak of World War II, the U.S. government bought every 520 that was still in the warehouse. Checked back into the arsenals at the end of the war, many were sent back into the field for Korea and Vietnam. A combination bayonet lug and 6-hole heat shield is mounted on the matching numbered barrel, with a plum tone and "S" stamp on the lug. It has a three-line address on the right side of the barrel and two-line gauge marking on the left, "P/(ordnance bomb)" proofs, cylinder choke and a 2 3/4 inch chamber. The frame is marked "P/(ordnance bomb)", "MOD. 520-30" and "U.S." and has the post-1920 upper tang safety switch and the locking block in the top of the frame. Smooth metal jacketed forearm and pistol grip stock with a green canvas sling, serrated plastic buttplate, and a 13 7/8 inch length of pull.