I looked at a database of Civil War soldiers and believe that I found your man, though the information does not exactly match the information that you had on that tag.
John Wells enlisted at age 18 on Febraury 8, 1865 at Holt, Mn., as a Private. He mustered in as a “Substitute” into Company G, 2nd Minn. Volunteer Infantry. He was hospitalized ( date and place not stated). Additionally, his date of mustering out is not listed on the Minn. Adjutant Generals Report. I do know that the 2nd Minnesota Volunteer regiment mustered out in July ‘65. I wonder if he participated in the 2nd Minn’s sweep through the Carolina’s (with Sherman) after the March to the Sea, or did he spend it in the hospital?