This is an Ithaca Model 37 riot gun with trench handguard attachment and "USSF" stamped on the lower left side of the receiver. The shotgun has a WWII pattern six-hole bayonet adapter with sling swivels on the heat shield and butt. The barrel and receiver have a gray, parkerized, finish. The stock and forearm are walnut with a military oil finish. The stock pistol grip and wrist have impressed checkering. The black plastic buttplate has impressed checkering and the Ithaca logo in the center. The left side of the barrel is roll-stamped with the two-line Ithaca legend followed by "CYL" and a "P" proofmark. A second "P" is stamped on the left side of the receiver near the barrel. Ithaca "Roto-Forged" logos are stamped on the right side of the barrel and receiver. The serial number is stamped on the lower right side of the receiver above the trigger guard. "U.S./X-213" is stamped on the bottom edge of the stock parallel to the buttplate. "X213" and "SP-30-06" are stamped on the right side of the bayonet lug. The significance of these markings is unknown. A nearly identical Ithaca Model 37 trench gun is illustrated on page 267 of "The Worlds Fighting Shotguns" by Thomas F. Swearengen with the caption: "Right side of an Ithaca Model 37 reportedly made for Army Special Forces".