CDV Armed Union Sargent
This sgt wears the 9 button dress frock coat and has his stripes on his sleeve. His sky blue pants have the NCO stripe as well. He wears the NCO belt with the 1851 belt plate and has what looks like a saber bayonet hanging from his side. Also he has a little pistol stuck in his belt.
No backmark but there is a pencil note to a person.