See Zalewsski & Falkiewicz.

Jerzy Falkiewicz designed and built an engine, together with Zalewski (see Zalewski & Falkiewicz) with two horizontally-opposed cylinders, that is, a small-power boxer for sports aviation.

"Jerzy Falkiewicz con su bicilindrico ligero"

-They constructed it in 1933, and called it "Bobo".