It looks similar to a Union naval uniform, although the buttons are small compared to other images and frock coats generally had nine pairs of buttons -- only seven visible here. Also there's a hint of a cuff ring that also suggests a naval uniform.
However, Army field officer (Major, Lieutenant Colonel and Colonel) frock coats had seven pairs, I believe.
It looks similar to a Union naval uniform, although the buttons are small compared to other images and frock coats generally had nine pairs of buttons -- only seven visible here. Also there's a hint of a cuff ring that also suggests a naval uniform.
Do you think this is the same guy? Hes the only Babbitt I can find in US records who was anything above a Corporal. Cant imagine that the uniform hes wearing in the OP would have been very appropriate for Ordnance? But what I know about uniforms you could fit on the head of a pin.