You are somewhat in luck. There were not many men by that name in Michigan units. (See list below.) However, it is unlikely that any of these Union soldiers carried a civilian weapon in the Civil War. More likely is that is was a personal civilian weapon from the Civil War era. What you have been told about the lock marking is correct, but with a much higher possibility of it being the lock maker's/marketer's name. You may be on a wild goose chase for a soldier that carried this rifle. There were MANY Wilkes involved in the gun trade...anyone of which may have made or marketed the lock.

1
Wilkes, Edward
10th Regiment, Michigan Infantry
Company D

2
Wilkes, Edward
27th Regiment, Michigan Infantry
Company not found.

3
Wilkes, George R.
2nd Regiment, Michigan Cavalry
Company C

4
Wilkes, John
1st Regiment, Engineers and Mechanics, Michigan
Company K

5
Wilkes, Nathan
2nd Regiment, Michigan Cavalry
Company C

6
Wilkes, Noah
17th Regiment, Michigan Infantry
Company H

7
Wilkes, Thomas A.
12th Regiment, Michigan Infantry
Company G

8
Wilkes, Thomas C.
12th Regiment, Michigan Infantry
Company G

9
Wilks, Archey
16th Regiment, Michigan Infantry
Company K & F

10
Wilks, Archey
16th Regiment, Michigan Infantry
Company I

You would need to research to see which (if any) of these companies came from that area of Michigan.