Here is a closeup of the Pony Express mailbag.  Each of the riders signed the bag as it moved through the states.
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/17578215@N00">Brett Neilson</a>
CC BY 2.0
<a href="//commons.wikimedia.org/wiki/Flickr" class="mw-redirect" title="Flickr">Flickr</a>: <a rel="nofollow" class="external text" href="https://www.flickr.com/photos/17578215@N00/572935926">Pony Express Mail Bag</a>