According other source: 113 Eskadra Mysliwska, 1 Pulk Lotniczy, Warsaw, 1939. Radio calling code 121-N was painted in black on the under surfaces of both wings. Signs of this regiment were painted on both sides of the fuselage and a white stripe on the upper surfaces of the right wing. After the German invasion of Poland was no more time to colour the planes in new paint scheme, so only upper national insignia, fuselage emblems and radio calling codes were painted off.
Poland | Military
PZL P.11 | 8.39, 121-N | 10