Crop of page 160 of the 1951 Pitt student yearbook. This work was originally published before 1964 apparently without any copyright notification or mark. Even if it had been copyrighted, the copyright would have needed to be renewed sometime in the 28th year. If the copyright was not renewed the work is in the public domain.
Renewals for copyrights from 1951 onward (and some, but not all, renewals for 1950 copyrights), as well as original registrations from 1978 onward are available online from the Copyright Office's Copyright Records web site. The initial search for a copyright was performed at that location. Since it is also best to search 6 months before and after the required year because some periodicals are published the month before the cover date and some registrations may be delayed for a few months, an additional search for copyright renewals cataloged in 1977, as well as those in 1978 that were not entered into the electronic database system, was performed here.
Originally this issue of The Owl was seemingly published without a copyright notice, but if it was copyrighted in 1951, this issue of The Owl student yearbook would have had to be renewed in 1978. Online searches of both the Copyright Office's Copyright Records web site and at the catalog of copyright entries for The Owl itself, editor Leizer Balk, business manager Jerry Simon, or the University of Pittsburgh revealed no renewal entries.
The Owl was not copyrighted, or a copyright of the yearbook was not renewed, and therefore it is in the public domain according to either criteria.
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.
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.