(a) The notes or bonds shall be executed by the president or chair and secretary of the board.
(b) The coupon attached to the bonds may be executed by the facsimile signature of the president or chair.
(c) In case any of the officers whose signatures appear on the bonds or coupons shall cease to be officers before delivery, the signatures shall nevertheless be valid and sufficient for all purposes, the same as if they had remained in office until the delivery.