Hi Charles, I have found and scanned the Rudorffer Fw190A-4 photo, so here it is. Rudorrfer was the Staffel Kapitan of 6/JG 2. Squadron leader of the 6th Squadron.
A brief description is therefore in order to explain....A German Geschwader or Fighter wing consisted of (at this time) 9 staffels or squadrons, they in turn were divided into 3 Gruppen or Fighter Groups.
The first 1,2,3 Staffel, second 4,5,6 the 3rd 7,8,9. So 6/JG 2 was part of II/JG 2, each staffel used coloured numbers to identify them.
White for the first, that is 1,4 and 7, Black for the second 2,5 and 8, finally yellow for the last staffel in each Gruppe, 3,6 and 9.
The second Gruppe carried a horizontal bar behind the fuselage cross and the third Gruppe a vertical bar, the first Gruppe had no marking in this position.
Your previously mentioned circle marking was introduced as a 4th Gruppe identification when 10,11 and 12 staffels were introduced to expand the Geschwadern.
Further changes occurred, but I will leave that for another time....
I have included a photo and profile of the 4th Staffel's commander Kurt Buhligen, the photo confirms the use of the white fuselage and wing ID bands as well as the yellow rudder and cowling underside, which are not visible on the Rudorffer photo. Buhligens aircraft, however still carries the European Grey camo rather than the desert camo portrayed in the Rudorffer profile back on page 1 of this thread.
Hope this helps you with the painting process.