Dark blue wool with applied white wool cooks cap construction.

Those soldiers with a modicum of culinary skills usually ended up preparing food although the Army provided no formal training during most of the nineteenth century. Finally in 1896 the Commissary General of Subsistence published its Manual for Army Cooks that simply doveimnto the details of cooking without any introduction.

Those that  were designated as cooks wore this cloth with the cooks cap on both sleeves in the same location as other chevrons. The cooks caps were made in the basic branch colors for Infantry, Artillery, engineers, and ordnance. The patterns were actually cut out of wool material with steel dies for uniformity. 

This originates from an established collection of U.S. Army chevrons