Well, I still believe that the car is a NAG C4b. My guess was Hansa-Lloyd, because they formed the GDA together with Brennabor and NAG. But GDA did not believe in badge engineering. Au contraire they reduced the brand portfolios in order to avoid competition within the GDA. And I didn't find any traces of a NAG-like Hansa-Lloyd in my books, neither in Kubisch's "Hansa Lloyd", nor in Mayer's Lloyd book, nor in Neumann's "Norddeutsche Automobilpioniere".
Technically it would have been a Hansa-Lloyd 10/45 PS, but the only Hansa-Lloyd car in that period mentioned in literature is the 18/60 PS Treff-Ass.