315.12 Bonds, legal investments.—Bonds issued by a unit under the provisions of this law are hereby made securities in which all public officers and public bodies of the state and its political subdivisions, all insurance companies, trust companies, banking associations, investment companies, executors, administrators, trustees, and other fiduciaries may properly and legally invest funds, including capital in their control or belonging to them. Such bonds are hereby made securities which may properly and legally be deposited with and received by any state or unit officer or any agency or political subdivision of the state for any purpose for which the deposit of bonds or obligations of the unit is now or may hereafter be authorized by law.