pr. G.[O?] No. 9, Hd. Qrs. Hy. Arty

Could be

“ . . . 20 Oct. 1862 per Ord. No. 9 H. Quars. . . . “

See: https://www.fold3.com/image/271/65580674

My great Uncle, Pvt. Isaac Martin, Co. K, 43rd Tenn. Inf.