EC3/12 based at Cambrai-Epinoy. Even there is no insignia at that time with the FAF it was easy to recognize the squadron regarding the registration. Here you have '12-ZP' so it is 12° EC (Escadre de Chasse) and the 1st letter give the squadron Y was for EC 1/12 "Cambrésis", K was for EC 2/12 "Picardie" and Z was for EC 3/12 "Cornouaille" So she is from 3/12.