New Hampshire backmark – Unidentified Union Soldier
Possibly a New Hampshire Infantry officer based on the stripe on his trousers. What at first look appears to be a shell-jacket is actually a military vest, probably sky blue as would be the trousers, along with a light-colored shirt. A pocket-watch chain is present as well. The CDV is suspected to have been taken from an earlier image rather than life. Note the reversed buttons and the mat abrasions.