Hi, Thomas...
I think the aircraft in your photo is A1+CP. My reasoning for this is as follows:
The unit emblem under the cockpit has a dark band underneath the bomb. I believe this was red, and indicitive of the II.Gruppe, whose I/D colour was red. I am also aware, however, that at least one source suggests it as being the unit badge for the entire Geschwader, but this would then beg the question - why the need for a red horizontal band?
If, for a moment, we agree that it is II.Gruppe, then the Staffeln within II.Gruppe would have been 4. 5. & 6.Staffel. I would say we could discount 5.Staffel, as the letter 'C' is, in my opinion, clearly not red (5.Staffel I/D colour), so it would either be white or yellow. Personally, I think it's yellow. It doesn't seem quite as light as the white outline of the fuselage cross, and the front section of the propellor spinners, more often than not painted in the Staffel colour, seem darker in shade to the white background of the unit emblem, so I think they are yellow, thus pointing to the possibility of the letter 'C' being yellow as well, and therefore suggestive of the fact that the last letter would be the 6.Staffel indicator, 'P'.
This is only my opinion, though, and others may well disagree. Interesting photo, though...
.
Regards...
Paul