A pioneering American model diesel of 0.28 cuin (4.59 cc) displacement, manufactured by the Air-O Model Supply Co. of Hawthorne, California. Its production was confined to a two-year period from late 1947 through until mid-1949. Both aero and car versions were produced. The engines are very well made, and perform very well indeed. The full story of this interesting design may be found here on the "Model Engine News" (MEN) web-site.