British <a href="https://en.wikipedia.org/wiki/Royal_Naval_Air_Service" class="extiw" title="w:Royal Naval Air Service">Royal Naval Air Service</a> <a href="https://en.wikipedia.org/wiki/AD_Flying_Boat" class="extiw" title="w:AD Flying Boat">Air Department Flying Boat</a>
unattributed
undated; probably ca. 1917
<a href="https://en.wikipedia.org/wiki/File:Air_Department_Flying_Boat.jpg" class="extiw" title="en:File:Air Department Flying Boat.jpg">en.wikipedia</a>