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.
Uploaded a work by Kansas State University; no copyright notice from [https://archive.org/details/royalpurple1971unse/page/84/mode/2up Royal Purple, 1971] with UploadWizard