Hello as far as I can recall in my books it is a nz 500 from around 1935/6 but several things are altered like the frontfork which was a girderlike type in those days.
And it started its life definetly as a black bike
Ít will be a hell of a job to make it original again good luck with it.
look at
www.dkwclub.nl and maybe you will find something.
regards george the second