Damn, missed that DuPont mark. You're spot on on that.
"They may be of WWII manufacture, but shotguns were not used in combat in WWII."
On that, however, you're not spot on on.
The Ithaca Model 37, the Savage 520/Browning Auto-5, and the Winchester Models 97 and 12 were all used fairly heavily in the Pacific and the China-Burma-India theater during World War II. There's even indications that shotguns went ashore in the initial waves on D-Day on June 6 in the hands of troops specially trained to clear out German bunkers and communications trenches, sort of a hearkening back to what their Fathers were doing in World War I.
The Marine Corps alone took delivery of over 100,000 shotguns for use during the war, many for combat operations in jungle conditions. Army troops were also issued shotguns for their excursions in jungle warfare in the Pacific.
As in World War I, waxed paper shells proved to be problematic, especially in jungle conditions. It was often found that, upon opening a box of shells, they were already swollen from the sea journey and high humidity.
Late in the war the military began to once again contract for brass shot shells, which were issued during the last 18 months of war.
The shotgun didn't see nearly as much use in Korea as it had during World War II. The longer ranges and mountainous terrain didn't make Korea good territory for shotguns. They were still there, but mainly for guard purposes, although there were some calls for shotguns to be used in city fighting, such as the battle to retake Seoul. I have also found references to shotguns being issued to machine gun teams to be used in close range defense against Chinese/North Korean wave attacks.
Vietnam, on the other hand, was a shotgun paradise. Ithaca was a major supplier of shotguns for combat operations in Vietnam. By that time plastic hulls had largely replaced paper, so the brass shell was a thing of the past.
I used to work with a guy who spent considerable time in Vietnam. He had a picture of him with some of his buddies, taken during a sweep. He's carrying, believe it or not, one of the probably relatively few Winchester Model 97s that was still in inventory during the middle 1960s.
I think the main reason why so few people realize how heavily the shotgun was used during World War II is because there was no really catchy "back story" behind it as there was in World War I.
In WW I, of course, the Germans threatened to execute any American caught with a shotgun, while the Americans on the other hand threatened to execute any German caught with the saw-back bayonet.
The Germans withdrew the saw-back bayonet, but the Americans never withdrew the shotgun, and neither side executed anyone.
In fact, there's a passage in, IIRC, "All Quiet On the Western Front" that talks about how the protagonist, by then a grizzled front-line veteran, helps get newly arrived recruits up to speed, including taking the saw-back bayonet away from one.
