This would appear to be what is sometimes called a "Hobby Lobby" build. In the past, in order to "maintain their gunsmithing skills," some USMC MOS 2112s have had discretion/privilege to build 'gratis'/pro bono rifles or pistols, using civilian parts, provided to them by active duty USMC personnel or retired personnel. Back then they could drop off the parts at the Lobby of the PWS shop, and a few weeks later they pick up the completed project, often they are built at the home of a 2112, with maybe some machining done at the PWS shop. Given the lack of any finish wear on that rifle and scope, it was built using civilian parts presumably purchased by the deceased Major. (Nothing on that rifle appears to be any issued/USGI parts).
In recent years, USMC PWS leadership has sort-of frowned upon "Hobby Lobby" activities (long story from previous decade about someone abusing their privileges for profit motive). Anyhow, since you asked, I suspect its a Hobby Lobby rifle, likely built 'gratis' for the USMC Major in the 1990s or early 2000s based, on the vintage of the civilian stock and scope. The 2112 didn't go through the trouble of clip slotting the receiver, but the other build/bedding characteristics are what is seen on M40A1s. No idea what barrel could have been used, but possibly its a 1/12 twist barrel. (Schneider barrels have been used since the early 2000s, but for a Hobby Lobby build, its whatever was provided by the deceased Major back in the day. Hart, Krieger, Schneider, or ?).
It's too bad they didn't do the black oxide coating of the barrel, but it could be done by others if they have the right solution. Stainless steel can not be parkerized/phosphated - but it can be chemically darkened via the black-oxide process. Its somewhat caustic solution, and not all gunsmiths want to mess with that finish. Given it was likely originally built by a 2112 decades ago, I would try to find someone to do the "correct" black-oxide finish on the barrel.
Sounds like that rifle found a good home, and hopefully you will enjoy Bernie's gift to you in the years ahead. Its a keeper.