Where it is not necessary to have letters granted to administer a decedent's estate but it is desired to have a public record of his death, a certificate of death may be filed with the register except that where a certificate of death cannot be obtained the affidavit of a relative or other interested party may be filed with the register setting forth the decedent's name, residence, date, time and place of death, and age at death. The register shall index and record all such certificates and affidavits filed with him.