Curtiss NC seaplane.  Plane number four of four built, named NC-4, sometime after the translatlantic test flight, 1919.  Visible is the fourth pusher engine which was added for that flight.
USN
1919
<p>USN photo Scanned from Page 261 of the following book:
</p>
<cite class="book" style="font-style:normal" id="Reference-Burgess-2001">Burgess, Richard R. (2001)      <i> <a rel="nofollow" class="external text" href="http://search.barnesandnoble.com/booksearch/isbnInquiry.asp?z=y&amp;isbn=0883631024&amp;itm=2">U.S. Naval Aviation</a></i>, Levin, Hugh Lauter Associates, pp. 352pp  <small></small></cite>