Other information

The source webpage says "There are no known U.S. copyright restrictions on this image. The digital file is owned by the Cornell University Library which is making it freely available with the request that, when possible, the Library be credited as its source."

On the the other, right above that it says "Digital reproductions are provided for private study, scholarship and research use only and may not be downloaded for use in electronic or print publications (including web sites), exhibitions, or broadcasts, without permission."

The dedication to the public domain is by the (claimed) copyright holder (Cornell Library). The identity of the person who actually created it is lost to history. And it's not true that there are no conditions: the Library asked for credit as the source, optionally, if the user would be so kind.

This work is in the public domain in the United States because it was published in the United States between 1929 and 1977, inclusive, without a copyright notice. For further explanation, see Commons:Hirtle chart as well as a detailed definition of "publication" for public art. 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. العربية ∙ беларуская (тарашкевіца) ∙ čeština ∙ Deutsch ∙ Ελληνικά ∙ English ∙ español ∙ français ∙ Bahasa Indonesia ∙ italiano ∙ 日本語 ∙ 한국어 ∙ македонски ∙ Nederlands ∙ português ∙ русский ∙ sicilianu ∙ slovenščina ∙ ไทย ∙ Tiếng Việt ∙ 中文（简体） ∙ 中文（繁體） ∙ +/−