Any municipality or any board, commission, or other authority established by ordinance of any 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 municipality, or the board of trustees of any retirement system created by the General Assembly of the State of Arkansas, may, in its discretion, invest any of its funds not immediately needed for its purposes in bonds issued under the provisions of this chapter. Bonds issued under the provisions of this chapter shall be eligible to secure the deposit of public funds.