Chevrolet via The Pat McDermott Company. It was not unusual for networks, program sponsors or studios to use either ad or public relations agencies to distribute publicity material. In this case, the show's sponsor, Chevrolet, used their public relations agency for this purpose.
Note that it may still be copyrighted in jurisdictions that do not apply the rule of the shorter term for US works (depending on the date of the author's death), such as Canada (50 p.m.a.), Mainland China (50 p.m.a., not Hong Kong or Macao), Germany (70 p.m.a.), Mexico (100 p.m.a.), Switzerland (70 p.m.a.), and other countries with individual treaties.