Pre-1978 no mark. The item was published in 1936 on a lobby card for the film. That publication had no copyright markings on it, as can be seen in the links above. At lower right is Country of Origin USA.
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=Scene from the 1936 film ''Romeo and Juliet''. Pictured are John Barrymore, Leslie Howard and Basil Rathbone. |Source=[http://31.media.tumblr.com/d39ef01282ef3d222c5b2e378222db81/tumblr_mp42w9Q9ik1rwq44lo2_1280.jpg source] |...