I have identified him. He is Fielding A. Patterson, born and raised in Key West, Florida, son of Alexander Patterson; was a 1st Lieutenant in the 6th N.Y. Cavalry under Col. Devins; was honorably discharged in Sept. 1862, and was commissioned by Virginia's loyalist Governor Peirpont to recruit a company of scouts in Loudoun and Fairfax County, Virginia; worked with Capt. Means of the Independent Loudoun Rangers. Was captured by Confederate forces at Winchester on June 15, 1863, and was imprisoned for almost two years, at a severe cost to his health. After the war he lived in the City of Washington, Virginia, Georgia, Tennessee, and Florida. He died Oct. 1, 1890.
I am still seeking more information on his family, etc.