With the help of a fellow collector, I was able to identify this guy as a USMC serving in the Civil War.
He wears a regulation 7 button frock coat with two cuff buttons and the white buff leather. His SGT stripes are inverted and while I cannot discern the letter "M" in the bugle-- there is definitely something in the badge:
Photograph is by Prince of New Orleans, so this guy appears to have served in one of the gulf coast ships.
I am not attached to this one, so it will probably go to the for sale section in the next few weeks.