Okay, I think I may have found the answers to my questions on eBay.
http://cgi.ebay.com/US-Army-Clothing-Bag-P...1QQcmdZViewItemQouted from the auction-
US ARMY CLOTHING BAG, PATTERN 1874
This pattern was introduced in 1878 (Type 3) made of tan cotton duck, with web binding throughout and a tinned button rather than the previous eagle button to close the inner rectangular meat can pocket. Shoulder strap made of drab webbing, fastens to the bag by means of two brass wire buckles attached through leather billets and adjusted to length by means of a Chambers buckle. Inside flap clearly marked, "WATERVLIET ARSENAL". Originally intended for use and wear on the 1874 brace system, a shoulder strap was made available in 1875 as new recruits had no need of the Palmer brace and a knapsack was not available. The clothing bag carried the soldiers' belongings and was worn slung over the shoulder, like the haversack. The cover is marked with a large, "US", and the soldier has applied his initials of ownership twice. A stain scattered along the top of the flap, otherwise, this clothing bag in excellent condition, as is shoulder sling. Bag measures 9 1/2" wide, 12" deep. Pocket 6 3/4" wide, 5 1/4" deep and expands bellows fashion, 1 1/2". The pocket also meant to carry an extra carton of .50-70 cal. ammunition.