The state and all counties and cities and other municipal corporations, political subdivisions and public bodies, and public officers of any thereof, all banks, bankers, trust companies, savings banks and institutions, building and loan associations, savings and loan associations, investment companies, insurance companies and associations, and all executors, administrators, guardians, trustees and other fiduciaries may legally invest any sinking funds, monies or other funds belonging to them or within their control in any revenue bonds issued pursuant to this act.