The M-1878 blanket bag replaced the Model 1874 Clothing Bag, and was designed to be worn on the soldier’s back like a rucksack or backpack. It was designed to be of sufficient size to carry the soldier’s bedding blanket, an extra pair of shoes, underclothing and socks, and his personal effects. A soldier or Marine could also attach his rolled shelter half and poncho to its exterior. Officially used until replaced by the blanket roll circa 1904, many of these bags remained in service and were still being issued during the mobilization for World War One by the United States in 1917. US Marines also used this bag, with photos extant of them wearing this bag on their way to Vera Cruz in 1914 (the Dept of the Navy apparently redesignated these the M-1912, see last image). The Model 1878 Blanket Bag is far less commonly found than the clothing bags and haversacks.
The cover has a clear "U.S." stencil, the interior of the front flap is stenciled “ROCK ISLAND ARSENAL” (with no date) and the exterior (against the back) is stenciled "MINNESOTA."
Photo Credit : Here