[GrzegorzM]

Very interesting, thanks!
Had de redesignation immediate effect (eg. in plane markings, code numbers?). I've heard that I.JG21, some time before the war turned into part of JG54, was still known with the old designation even in official documents.

And anybody can check the code number of Mazurowski's airplane, and exact version (some say that it was 110B, and some that it could have been 110C). Are the exact airplane versions for Sept. 1939 in that unit known?

Thanks in advance!
G.

P.S. my German friend wrote to me:
"this Bf110B was from 3.Staffel , I.(Z)/ LG 1. This means it was from the Zerstörerstaffel des Lehrgeschwaders 1.

Verbandskennung (Unit Code) of LG 1 was L1

The Staffelbuchstabe of the 3.Staffel was D
(A = Stab = green
B = 1. Staffel = white
C = 2. Staffel = red
D = 3. Staffel = yellow
E = 4. Staffel = blue).

So it very likely that this Bf 110B was painted in standard 70/71/65 colors and marked with L1+?D. The unknown letter aft of the cross (the aircraft's letter) should be yellow or black with a yellow line."