1921:- MB-3 converted to 1pOhwM; 400hp Wright-Hisso H-3 (>585hp Packard 1A-2025); span: 29'0" length: 25'0" v: 155; ff: 9/29/22 (p: Capt Frank O Hunter). Strut-braced, gulled, parasol wing. POP: 2 as R-5 military entries in 1921 Pulitzer races; [AS64373=A6070] (dropped out with lubrication problems) and [AS64374=A6071] (destroyed in crash during trial flight). One reportedly tested with 400hp Curtiss D-12, both subsequently destroyed in static testing.

This aircraft took part in the 1922 Pulitzer Trophy Race.