Donald A. Hall Sr. Beside Proprietary Low-Wing Monoplane X7621 (Plate #6088) (Circa 1928)

Donald A. Hall standing beside the tail of his proprietary low-wing monoplane X7621 on an airfield. — Donald A. Hall Sr. Beside Proprietary Low-Wing Monoplane X7621 (Plate #6088) (Circa 1928) · Donald A. Hall Estate Collection

An archival master negative plate (#6088) documenting Donald A. Hall Sr. standing alongside his proprietary low-wing monoplane (registration X7621) at Dutch Flats in San Diego. The image details the aircraft's empennage geometry, balanced rudder with bold civil registration numbers, external tail bracing, and fabric-covered fuselage structure. In the background, the radial engine, cockpit fairings, and high-aspect-ratio low wing illustrate Hall's post-NYP research into advanced monoplane efficiency.