The treasurer of the said cities shall be the custodian of the several funds. All payments from said funds shall be made by him only upon vouchers signed by two persons designated by the board of trustees. A duly attested copy of the resolution of the board of trustees designating such persons and bearing on its face specimen signatures of such persons shall be filed with the treasurer as his authority for making payments upon such vouchers. No voucher shall be drawn unless it shall previously have been allowed by resolution of the board of trustees.