The township board in counties under township organization is authorized and instructed to direct the county treasurer to invest the sinking fund of the township in the custody of the county treasurer in the warrants of the township. The investment of the sinking fund shall be limited to warrants of its own issue. Upon an order of the township board properly signed by the supervisor and countersigned by the township clerk, the county treasurer shall invest the sinking fund for the benefit of the township as provided in this section.