An official record kept within the United States, or any state, district, commonwealth, territory, insular possession thereof, or the Panama Canal Zone, the Trust Territory of the Pacific Islands, or the Ryukyu Islands, or an entry therein, when admissible for any purpose, may be evidenced by an official publication thereof or by a copy attested by the officer having the legal custody of the record, or by his deputy, and accompanied by a certificate that the officer has the custody. The certificate may be made by a judge of a court of record having jurisdiction in the governmental unit in which the record is kept, authenticated by the seal of the court, or by any public officer having a seal of office and having official duties in the governmental unit in which the record is kept, authenticated by the seal of his office.