Panama-Pacific commemorative coin issue
... that the octagonal $50 piece of the Panama-Pacific commemorative coin issue is the only U.S. coin that is not round?
... that the octagonal $50 piece of the <b id="mwAg8"><a class="mw-redirect" href="./Panama-Pacific_commemorative_coin_issue" id="mwAhA" rel="mw:WikiLink" title="Panama-Pacific commemorative coin issue">Panama-Pacific commemorative coin issue</a></b> <i id="mwAhE">(pictured)</i> is the only U.S. coin that is not round?