Any municipality or county, or any board, commission, or other authority thereof, 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 any county, or the board of trustees of any retirement system created by the General Assembly may, in its discretion, invest any of its funds in the revenue bonds issued under the provisions of this subchapter, and revenue bonds issued under this subchapter shall be eligible to secure the deposit of public funds.