Boeing Y1B-17A, serial number 37-269.
U.S. Air Force
late 1930s <div style="display: none;">date QS:P,+1930-00-00T00:00:00Z/8,P4241,Q40719766</div>
<a rel="nofollow" class="external free" href="https://media.defense.gov/2006/Jun/01/2000554876/-1/-1/0/060515-F-1234S-002.JPG">https://media.defense.gov/2006/Jun/01/2000554876/-1/-1/0/060515-F-1234S-002.JPG</a>, from <a rel="nofollow" class="external text" href="https://www.nationalmuseum.af.mil/Upcoming/Photos/igphoto/2000554876/">gallery page</a>.