Since this comic book was first published in the U.S. before 1964, the original copyright lasted 27 years from the end of the year of first publication. The copyright holder was free to renew the copyright any time during the year 1977, but they did not do so. (All copyright renewals after 1977 can be searched online here.) The copyright has expired.'
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.