This is a pair of buckskin breeches. A pair like this might be work by a Cavalry or Dragoon soldier, where the strength and durability of buckskin would serve them well when crafted into breeches and worn when riding. For source and more details, click here.
Image from: http://www.nps.gov/history/museum/exhibits/revwar/image_gal/vafoimg/frameshell.html