Mich. Comp. Laws § 141.32

Sec. 2. The county treasurer, the county clerk, the register of deeds, the chairman of the board of supervisors and the chairman of the finance committee of the board of supervisors of the several counties of this state shall constitute and be a board of sinking fund commissioners: Provided, however, That in counties having a board of auditors, the board of sinking fund commissioners shall consist of the county treasurer, the county clerk, chairman of the board of supervisors and the chairman of the board of county auditors.