Any county or municipality or any board, commission, or other authority established by ordinance of any county or municipality or the boards of trustees, respectively, of the firemen's relief and pension fund and the policemen's pension and relief fund of any such municipality, or the board of trustees of any retirement system created by the General Assembly may invest any of its funds not immediately needed for its purposes in bonds issued under this chapter, and bonds issued under this chapter shall be eligible to secure the deposit of public funds.