Note: Although the series only aired in the late 60s, this episode was registered for copyright in 1961 [1], but the copyright was not renewed.
Copyright Renewal Act of 1992 102. (g) - "The amendments made by this section shall apply only to those copyrights secured between January 1, 1964, and December 31, 1977. "
It also contained the year 1962 in the copyright notice.
2104: ...(The Copyright Renewal Act of 1992) "does not apply to such works" (published between 1964 and 1977) "when they were first published with a year date in the copyright notice that is earlier than 1964.
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 (70 years p.m.a.), Mainland China (50 years p.m.a., not Hong Kong or Macao), Germany (70 years p.m.a.), Mexico (100 years p.m.a.), Switzerland (70 years p.m.a.), and other countries with individual treaties.