The copy on the back of this photo indicates that while it was originally taken in May 1937 by AP photographer Murray Becker, this copy of the 1937 photo was sent by AP in December 1956 for a feature story to be done on the twentieth anniversary of the Hindenberg crash that was printed Janauary 2, 1957.
Original registrations were checked in art work for the year 1937. There were no registrations for Associated Press.
Renewals for the original copy of the photo taken in May 1937 were checked in art work for the years 1964 and 1965. There were no renewals for Associated Press.
Since the photograph was re-issued by Associated Press in December 1956 for a January 1957 story on the twentieth anniversaty of the disaster, original registrations were checked in art work for 1956. There were no registrations for Associated Press.
A renewal search regarding the 1956 re-issue of the photo was done at copyright.gov for Associated Press. There were newer original registrations for the company, but only one renewal for the time frame 1964-1965, which would apply to the original photo. The renewal was for material related to Winston Churchill. There were no renewals for the time frame 1983-1984, which would apply to the re-issued photo.
There's no evidence that copyright was filed for either the original 1937 photo or the 1956 re-issue of it, but I will re-license this as copyright not renewed to be certain of a proper license.
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.