High Standard 20-6 K-1200 Military Shotgun?????

I live near Quantico Virginia and purchased this High Standard Shotgun from a widow who was cleaning out the family home prior to moving. I was referred to because I have an FFL and am a former Marine Officer. Her husband had been a career Marine in the Korea/Vietnam era (Master Gunnery Sergeant. I agreed to research it and if it was correct, increase my purchase price accordingly. The piece was wrapped in old towels in an upstairs closet and she said that he had it for over 30 years. As the pictures indicate it is a High Standard 20-1 K-2000 .Left side of the receiver has the Serial umber "14XXX." It is parkerized and has an Ordnance Bomb on the top of the barrel. There is a" P" stamped on the bottom of the barrel near the receiver. The sling attachment points which appear to be factory. The bottom of the pistol grip has the numbers 11 67. On the right side of the stock there is a stamp about an inch in diameter with the "Eagle, Globe and Anchor" and the words "Marine Corps" in small letters. They were very hard to see and I took a little denatured alcohol to clean the wood . The trigger guard has some wear like it was filed to put in a rack. I did some research to include Canfields book and web searches which indicate that in addition to HS Trench Guns submitted to be tested there were also some riot guns purchased and these went to the Army, USAF and Navy. I will try and get detailed info on her husband. The area always turns up a lot of good stuff.... Being close to Quantico Marine Base and FBI Academy, the Dale City gun show back in the 1990s and early 2000s had lots of nice walk ins. And the question is..... Is it an old fake? Thanks

Will check it out tomorrow... there is a You Tube Video on HS shotguns that show pages from the old book on Combat Shotguns and it says that the test model did not have removable barrels. This one has a fixed barrel. Also, if you look at the stock sling attachment it looks like it if from a 1903 because it is offset to one side.

Todd,

The pages posted are from the book I was referring to. No date on sling and nothing under the buttplate. Do HS shotguns usually have removable barrels because this one is threaded on.