The only other possibility was a W.H. Hubbard of the 27th Indiana Infantry.
I can't be positive but there is one other photo of a 137th Ill. soldier
( 1st Sgt. Thaddeus Huston ) with the same oval design
that is pictured on the American Civil War Database
Residence Pittsfield IL; Enlisted on 6/5/1864 as a 2nd Lieutenant. On 6/5/1864 he was commissioned into "H" Co. IL 137th Infantry He was Mustered Out on 9/24/1864