Palazzo Socci, Florence. Actual owners of Palazzo Socci are descendants of the Chiaramonti family from Cesena, and they own several memories of their pope Pius VII. So this autograph is very likely to be original.
<a href="//commons.wikimedia.org/wiki/User:Sailko" title="User:Sailko">Sailko</a>
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<span class="int-own-work" lang="en">Own work</span>