The corporal in the photograph was in the Monroe Light Guard. My issue being that it looks like he has a "B" on his kepi. The Monroe Light Guard became company B, 7th Michigan Volunteer Infantry Regiment but they were not Company "B" in their pre war Militia regiment. It is possible that when this corporal arrived at the Camp of Instruction and his company was designated Company "B" of the 7th Michigan that he some how obtained a brass "B" and put it on his militia kepi. Another possibility is that this is his gray uniform issued at the Camp of Instruction as it seems to match the written description of the Camp of Instruction issued uniform and I know that company brass letters were also issued there. Also two NCOs in other regiments which attended the same Camp of Instruction were photographed in what appears to be matching uniforms. What are the odds that the State of Michiagn had uniforms made for issue at the Camp of Instruction that match the uniform the pre war Monroe Light Guard wore? This can not be entirely ruled out, but seems a bit too convenient.
I have been told I am "stupid" to believe this to be the uniform worn at the Camp of Instruction. I still believe my theory is more likely.