The corporate authorities of any such city or village may make provision by ordinance for the conservation of the money paid under the foregoing sections of this Division and the income therefrom through the means of a duly accredited National or State bank acting as trustee of the fund created thereby and making payments therefrom at stated intervals to such family or dependents.
     In the event any such corporate authorities shall make provision by ordinance for the conservation of the money by the naming of a State or National bank to act as trustee, such ordinance may specify the general classes of securities, including tax warrants, in which such trustee may invest such fund. It shall be unlawful for the trustee to invest the same in any other class of securities except such as are so specified.