All funding bonds shall be signed by the treasurer of the district, attested by the secretary, and shall have the official seal of the district affixed thereto. The form of the interest coupons attached to the funding bonds shall be determined by the treasurer subject to the approval of the board of directors. The signature on the interest coupons shall be that of the treasurer and may be either written, or an engraved or printed facsimile. The principal and interest of the funding bonds shall be payable in lawful money of the United States of America at the office of the treasurer of the district issuing the same.