I find it difficult to believe he was ever at Camp Staunton, Maryland. As near as I can tell his regiment served as guard troops at Andersonville, Georgia with Col. Fannin as commandant of all troops there.

George Martin

Private William Mattox, age 47, enlisted April 25, 1864 at Atlanta, in Company B, 1st Regiment Georgia Reserves (Fannin's), died October 25, 1864

See also: http://www.geocities.com/csareserve1/index.html