During World War II, Stevens began producing both the Model 520A (renamed the Model 520-30) and the Model 620A (labeled as the Model 620) as trench guns, riot guns, and long-barreled training guns for the US military.
 Trench guns were produced with 20-inch barrels (cylinder bore) and had heat shields with unique pinkish anodized bayonet lugs attached to the front (late war examples had a small "S" stamped on the left side).
 
The receivers of both models were stamped on the left side (from front to back) with a small "P" and ordnance bomb, "Model 520-30" or "Model 620", and a small "U.S." over the trigger.
Model 520-30 trench gun barrels are marked "Proof Tested--12 Gauge --2 3/4 Inch Chamber--" on the left side and have another small "P" and ordnance bomb and the "J Stevens Arms Company" address on the right side of the barrel.
 This was done so that all the markings could be read with the heat shield installed.
 Some Model 620 trench gun barrels were marked in the same manner as the Model 520-30 trench guns and some had all the barrel markings on the left side.
 Trench guns were also fitted with a sling swivel in the stock.
 Riot guns also had 20-inch barrels (cylinder bore) and had all the same martial markings, except that all the barrel markings were on the left side.
 The long barreled training guns were marked in the same manner as riot guns and were mainly used for aerial gunnery training.
 Total wartime production of all Model 520-30 shotguns was 33,306 and all Model 620 shotguns were 12,174.
 
After the war the US military standardized both the Model 520-30 and the Model 620 and kept them in the inventory.
 They were used in the Korean War and as late as the Vietnam War.
During World War II, Stevens began producing both the Model 520A (renamed the Model 520-30) and the Model 620A (labeled as the Model 620) as trench guns, riot guns, and long-barreled training guns for the US military.  Trench guns were produced with 20-inch barrels (cylinder bore) and had heat shields with unique pinkish anodized bayonet lugs attached to the front (late war examples had a small "S" stamped on the left side).  
The receivers of both models were stamped on the left side (from front to back) with a small "P" and ordnance bomb, "Model 520-30" or "Model 620", and a small "U.S." over the trigger. Model 520-30 trench gun barrels are marked "Proof Tested--12 Gauge --2 3/4 Inch Chamber--" on the left side and have another small "P" and ordnance bomb and the "J Stevens Arms Company" address on the right side of the barrel.  This was done so that all the markings could be read with the heat shield installed.  Some Model 620 trench gun barrels were marked in the same manner as the Model 520-30 trench guns and some had all the barrel markings on the left side.  Trench guns were also fitted with a sling swivel in the stock.  Riot guns also had 20-inch barrels (cylinder bore) and had all the same martial markings, except that all the barrel markings were on the left side.  The long barreled training guns were marked in the same manner as riot guns and were mainly used for aerial gunnery training.  Total wartime production of all Model 520-30 shotguns was 33,306 and all Model 620 shotguns were 12,174.  
After the war the US military standardized both the Model 520-30 and the Model 620 and kept them in the inventory.  They were used in the Korean War and as late as the Vietnam War.
Stevens Model 520/620