Man, these bags slap. 
 
Made of rubber vinyl, these will keep whatever you keep inside dry. These were made to carry either the SM-67 gas mask or the SM-74. Both appear the have been carried in this bag. 
These close via 2 snaps and would be carried with an adjustable shoulder strap. 
The shoulder strap can be clipped on the bag to either be worn horizontally or vertically. 
 
These measure about 12in x 10in
 
These are used to expect some staining, fading, or added markings. Aside from that, these are all ready to be used.