This is an example of a gentleman’s queue bag. It would be worn to hold a man’s hair or wig that flowed onto their shoulders, keeping it more closely tied together. It would help to protect, and keep clean, their collars and clothing. It is make od silk and linen, and measures around 4.75″ x 10″. For source and more details, click here.
Image from: http://www.cr.nps.gov/museum/exhibits/revwar/image_gal/morrimg/bagquequ.html