Note that although the film is dated to 1964, it contains the year 1963 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.