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