Evidences of indebtedness must be executed by a member or members of the commission as designated by the commission, or by facsimile signature and the manual signature of a     designated authenticating agent. Any evidences of indebtedness bearing the signature of members in office at the date of signing are valid and binding for all purposes notwithstanding that before delivery any person whose signature appears on the evidences of indebtedness has ceased to be a member.