Since this is the only copy of the poster I could find at present, and it isn't large enough to be able to determine whether there are copyright markings on it or not, A search of copyright renewals was done in both motion pictures and artworks for the years 1956 and 1957. There were no listings for the title under Motion Pictures and no listings for Tiffany Films under Artwork. There's no evidence of copyright for the film and for the poster, if the poster was ever copyrighted at all.
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.
{{Information |Description=Poster for the 1920 film ''Border Romance''. |Source=[http://movieposters2.com/images/783357-b.jpg source] |Date=[http://www.imdb.com/title/tt0019711/ 1929] |Author=Tiffany Films |Permission=Copyright not renewed |other_versi...