Postally unused. Title reads: "De Petrowski in Sommer Biplane - wing surface 36 sq m, 10 m wing span, total weight 320 kg, with a 50 hp Gnome engine, having only a vertical surface (?)". Very good condition.
Postally unused. Title reads: "De Petrowski in Sommer Biplane - wing surface 36 sq m, 10 m wing span, total weight 320 kg, with a 50 hp Gnome engine, having only a vertical surface (?)". Very good condition.
