Public domain works must be out of copyright in both the United States and in the source country of the work in order to be hosted on the Commons. If the work is not a U.S. work, the file must have an additional copyright tag indicating the copyright status in the source country. Note: This tag should not be used for sound recordings.PD-1923Public domain in the United States//commons.wikimedia.org/wiki/File:W1YK_ARRL_Charter.jpeg
Scanned in this copy from WPI's (Worcester Polytechnic Institutes) archives.
As this is simply a digital scan of the original from 1920, it falls under public domain as this was made before January 1, 1923.