Pre-1978 no mark. There are no copyright markings pertaining to the image as can be seen in the links above. At bottom is Country of origin USA and A (looks like 12144); this seems to refer to the print job 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 (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 1930 film ''Aping Hollywood''. |Source=[http://www.ebay.com/itm/Tiffany-Chimps-Aping-Hollywood-1930-039-s-27x41-Linen-Backed-Poster-All-Monkey-Cast-/281503145674?pt=LH_DefaultDomain_0&hash=item418ae51eca&nma=tr...