(1) Bonds issued under this chapter may be executed by the facsimile signature of the chairman of the authority issuing the bonds and by the manual signature of the secretary of the authority issuing the bonds and sealed with the seal of the authority issuing the bonds.
(2) The coupons attached to the bonds may be executed by the facsimile signature of the chairman of the authority issuing the bonds.
(3) In case any of the officers whose signatures appear on the bonds or coupons shall cease to be such officers before the delivery of the bonds or coupons, their signatures shall, nevertheless, be valid and sufficient for all purposes.