If any officer whose signature, countersignature, or attestation appears on any district bonds or coupons thereof, ceases to be such officer before the delivery of the bonds to the purchaser thereof, such signature, countersignature, or attestation shall nevertheless be valid and sufficient for all purposes the same as if such officer had remained in office until the delivery of the bonds. The signature upon the coupons of the person who is county auditor at the date of such bonds shall be valid although the bonds themselves may be attested by a different person who is county auditor at the time of delivery of the bonds.