The Medal of Honor was a Union invention. The Roll of Honor is explained in Wesley Leeper's 1964 history of the 2nd Arkansas Mounted Rifles, "Rebel's Valiant" and 1st Sgt. H.M. Graves was indeed selected for Company "I". Leeper further reports that Sgt. Graves was captured at Columbia, TN during the retreat from Nashville, Dec. 22, 1864. On June 6, 1865 he was released at Point Lookout, Maryland, after signing the Oath of Allegiance. The 3 Graves soldiers are listed as you mentioned, Henry M., John B., and Mark H.