Martin MB-1 GMC (Glenn Martin Cannon), Army Air Service serial number 62951, front view with 37mm nose cannon.
USAF
U.S. Air Force photo <a rel="nofollow" class="external autonumber" href="https://media.defense.gov/2006/May/11/2000557463/-1/-1/0/060420-F-1234P-031.JPG">[1]</a> from the <a rel="nofollow" class="external text" href="http://www.nationalmuseum.af.mil/Upcoming/Photos/igphoto/2000557463/">image gallery</a> on the website of the National Museum of the United States Air Force.