[vinnie]

Thanks for the reply, John!
It seems that Miksch flew in black 20 Werk Nr. 15429 since he entered 8./JG 1 (most likely july 1943); he poses in front of it, and at that moment the rudder shows 37 victories (Mombeek, p. 165). Other pictures from the summer of 1943 indicate that Miksch also flew black 5 at the same time. Interesting to note is that the Mombeek book shows black 5 with a small 5, and another picture (small picture, a little higher than the bottom picture) shows a bigger black 5, with white outlining (p. 164). The latter version was common practice in 8./JG 1 in this period.
It could be that black 5 was the same aircraft as black 20, though it looks like if black 20 became Miksch' Me-109 in july 1943, and in the same period he also used black 5. Perhaps he started flying in black 13 from 8 october and on (till 1 December 1943).