All securities of an authority shall be signed in the name and behalf of the authority by its chairman or vice-chairman, and the seal of the authority shall be affixed thereto and attested by its secretary or an assistant secretary; provided, that a facsimile of the signature of one, but not both, of the officers whose signature will appear on such securities may be imprinted or otherwise reproduced on any thereof in lieu of his manually signing the same; and provided further, that a facsimile of the seal of the authority may be imprinted, or otherwise reproduced, on any such securities in lieu of being manually affixed thereto. Any coupons applicable to any securities of the authority shall be signed either manually by, or with a facsimile of the signature of, the chairman or the vice-chairman of the authority. If after any such securities or coupons shall be so signed, whether manually or by facsimile, any such officer shall, for any reason, vacate his office, the securities and coupons so signed may nevertheless be delivered at any time thereafter as the act and deed of the authority.