i believe I have found the officer. Major John M. Wall was promoted from 1st Lt. of Co. G, 15th Tennessee Infantry. Polk appointed him assistant surgeon of the regiment. Apparently while serving as assistant surgeon, he was appointed acting ordnance officer for the division for a short period. He later would command the regiment. At Shiloh, the 15th Tennessee was in the 2nd Division of the 1st Corps, which matches the record in Pvt. Wahl's file.