English: Original theatre poster for a chapter of Adventures of Captain Marvel (1941).
The item has no copyright markings on it as can be seen in the link above. At bottom is Litho in USA, 41647 anf 51/8807. These look to be related to the printing of the poster.
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.