It kind of sticks in my mind because the shotguns were just the opposite. Army used Winchester shotguns and the Marines used Remingtons.
The Marines used the Remington 870 and the Army the Winchester 1200. The Marines got the better deal.
(just my opinion, but I think the Army stuck with Winchester because of the good results they historically had with the Win 97 and Model 12. Compared to them, and compared to the Rem 870, the Win 1200 is ...inferior. Its not a total POS, but it has flaws the others don't)
As to the M2HB, If I remember correctly there's a picture of one with the scope on it in one of the books about Hathcock. might be "Marine Sniper 93 comfirmed kills" but its been ages since I read it, and am not sure of the title anymore.
Many VietNam era M2s had a rear sight base made to accept the mount for a night sight (infrared I heard, never saw one in use). It's quite possible to have an adaptor fabbed to use the existing sightbase to mount a conventional scope. Alternately, the M2 rear sight is mounted with large screws, and it would only be a few minutes work with a screwdriver to replace the issue sight with a custom made scope base, and switch back when finished.
I took that internet quiz a while back, and yes, besides outright mistakes, the pictured firearm often has only a slight connection to the answer, or additional data in the answer.