03/15/2020. Remarks by Johan Visschedijk: "Designed by W.H. 'Glen' Warren of San Luis Obispo, California, USA, this stubby-looking aircraft was built as an aero engineering class project at the California Polytechnic School (presently known as California Polytechnic State University, popularly named Cal Poly) in Obispo. Powered by a 150 hp Comet 7D seven-cylinder air-cooled radial engine, it was flown in 1929. With the experimental registration X501M, it was registered to Glen Warren."