This is a tintype from 1863. Abner W. Tarbell is standing; he was a private. Sergt. James M. Tarbell is seated on the left. On the right is Thomas J. Tarbell, a Second Lieutenant identified by his bars. His hat has a diamond indicating the Third Corps, and also the letters 'S.S.' and two other letters I haven't figured out yet. S.S. stands for Sharpshooters.