The bonds of each series thereof issued pursuant to this article shall be sold by said authority at public sale as provided in Amendment 619. Said bonds shall be executed in the name of the state by the Governor and countersigned by the chairman of the authority, and the Great Seal of the State shall be impressed thereon and attested by the Secretary of State. A facsimile of the signature of each such official may be imprinted on any of said bonds in lieu of being manually inscribed thereon, and a facsimile of the Great Seal of the State may be printed on said bonds in lieu of such seal being manually impressed thereon. Each such facsimile signature shall be valid in all respects as if the officials whose facsimile signatures are so used had signed said bonds in person, and any facsimile of the Great Seal of the State so used shall be valid in all respects as if such seal had been manually impressed on said bonds. In the event any official who shall sign any of said bonds or whose facsimile signature shall appear thereon shall thereafter cease to hold office before such bonds are delivered and paid for, such bonds shall nevertheless be valid for all purposes to the same extent as if the official who signed such or whose facsimile signature appears thereon had remained in office until all of the bonds bearing such signature or facsimile thereof shall have been delivered and paid for.