The item has no copyright markings on it as can be seen in the links above. At bottom left is Litho in USA and {looks like #3766 or 3786). This appears to refer to the print job of the poster. At bottom right is Tooker Litho Co, NY--they printed 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 (50 p.m.a.), Mainland China (50 p.m.a., not Hong Kong or Macao), Germany (70 p.m.a.), Mexico (100 p.m.a.), Switzerland (70 p.m.a.), and other countries with individual treaties.
{{Information |Description=Poster for the 1937 film ''Navy Blue and Gold''. |Source=[http://www.ebay.com/itm/NAVY-BLUE-AND-GOLD-1937-ORIGINAL-LINEN-BACKED-1-SHT-POSTER-JAMES-STEWART-/111570616931?pt=LH_DefaultDomain_0&hash=item19fa208263&nma=true&si=dp...