1860 insignia of the corps of topographical engineers - used on Powell's second expedition. Design circa 1860. Grand Canyon National Park Museum Collection, P.O. Box  129, Grand Canyon, AZ 86023
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<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/grand_canyon_nps/4686937340/">17263 Grand Canyon Powell Expedition 1873</a>