Martin MB-2 (NBS-1) bombardier compartment with Estoppey D-1 bombsight, adjusted to compensate for wind drift.
USAF
U.S. Air Force photo <a rel="nofollow" class="external autonumber" href="https://media.defense.gov/2007/Feb/05/2000517126/-1/-1/0/070205-F-1234P-008.JPG">[1]</a> from the <a rel="nofollow" class="external text" href="http://www.nationalmuseum.af.mil/Upcoming/Photos/igphoto/2000517126/">image gallery</a> on the website of the National Museum of the United States Air Force.