And some more ... if the code was S9+AA for instance, it was the plane of the ZG1 Stab. In the case the ZG Stab (Staff/headquarters) Staffel ID letter ( the latest in the code ) was "A" and the individual letter was of blue. If it was an aircraft belonged to the Gruppe ( regiment ) Stab squadron the last letter was as listed below but the individual letter was of green.
I Gruppe - B
II Gruppe - C
III Gruppe - D
IV Gruppe - E
V Gruppe - F
Here is the Bf 109E-7/B of the Stab squadron of the III./ZG1 ... the green letter "C" is almost unnoticeable contrary to the "D" one that indicates the III Gruppe.
I Gruppe - B
II Gruppe - C
III Gruppe - D
IV Gruppe - E
V Gruppe - F
Here is the Bf 109E-7/B of the Stab squadron of the III./ZG1 ... the green letter "C" is almost unnoticeable contrary to the "D" one that indicates the III Gruppe.