Gov. Code, § 29928

If any officer whose signature, counter-signature, or attestation appears on any county bond or coupon ceases to be such officer before the delivery of the bonds to the purchasers, the signature, counter-signature, or attestation appearing either on the bonds or the coupons, or on both, is valid and sufficient for all purposes to the same extent as if the officer had remained in the office until the delivery of the bonds. The signature upon the coupons of the person who is auditor or treasurer at the date of the bonds is valid although the bonds themselves are attested by a different person who is auditor or treasurer at the time of their delivery.