Issued starting in mid-1942 to replace the complex and inefficient M1928 Haversack. It was made to carry the standard Marine combat load- meat can, utensils, spare socks and underwear, toiletries, and a basic load of rations. This bag was provided with attachment points to secure the entrenching tool and bayonet, as well as provisions to carry the shelter half and/ or poncho.
This upper pack was designed to attached to the “Lower” Bag” Knapsack. When both backs are attached along with “Suspenders this is known as the “782 Pack” system.
Above photos are from the collection of Don Abernathy
Photo and above info borrowed from Atthefront.com