In this image, it can be seen the unofficial patent symbol not currently used by the us patent office.
<a href="//commons.wikimedia.org/w/index.php?title=User:Alejitao123&amp;action=edit&amp;redlink=1" class="new" title="User:Alejitao123 (page does not exist)">Alejitao123</a>
2020-12-29
<span class="int-own-work" lang="en">Own work</span>