The bonds must be signed in the name of the board of the authority by the manual or facsimile signature of the chairman of the board and attested with the manual or facsimile signature of the secretary of the board. Interest coupons attached to the bonds must be signed by the facsimile signatures of the officers. The bonds may be issued notwithstanding that any of the officials signing them or whose facsimile signatures appear on the bonds or the coupons have ceased to hold office at the time of issue or at the time of the delivery of the bonds to the purchaser.