This poster was created before 1977, and does not have a copyright notice on it. It therefore qualifies as Public Domain under w:WP:NFC: "If a work has no copyright or is licensed to Wikipedia under an acceptable "free" license, it is a free work and may be used on Wikipedia without copyright concerns."
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.