Section 321 - Certificates of service1. In any proceeding under this act a certificate executed by an officer of the applicable force of the armed forces of the United States or by an officer of the applicable force of the organized militia shall, when produced, be prima facie evidence of the facts therein certified and of the authority of the signer to issue the same.2. When a person in military service has been reported missing he shall be presumed to continue in such service until accounted for, and no period herein limited which begins or ends with the death of such person shall begin or end until the death of such person is in fact reported to or proved by the applicable force of the armed forces of the United States or of the organized militia, or until such death is proved by a court of competent jurisdiction; provided, that no period herein limited which begins or ends with the death of such person shall be extended beyond a period of six months after the time when this act ceases to be in force.