This signature is believed to be ineligible for copyright and therefore in the public domain because it falls below the required level of originality for copyright protection both in the United States and in the source country (if different). In this case, the source country (e.g. the country of nationality of the signatory) is believed to be United States of America.
Note that this tag cannot be used on all signatures, as not all signatures are copyright-free.
This United States Congress image is in the public domain. This may be because it was taken by an employee of the Congress as part of that person’s official duties, or because it has been released into the public domain and posted on the official websites of a member of Congress. As a work of the U.S. federal government, the image is in the public domain.