This 'Ansitzsack' is a special German hunting accessory much like a short sleeping bag that extends over the hips and basically translates as a sitting sack. 
It is made out of extremely thick sheepskin. The wool side is left at its original length for maximum insulation. 
Used for sitting in the cold for long periods of time. Also great for those outdoor sporting events when extra warmth is needed. The shape is cut like an "S" so that there are no pressure spots while sitting. The zipper extends partially down the side creating an enclosed area for your feet.