With my compliments, MoGas, here's your personal mount.
The letters on the fuselage are not readily visible, but we know that the unit code for NJG 4 was 3C. The third letter may be an outlined "E." The letter identifying the
staffel is completely illegible, so I have your grandfather flying in the plane of the
Geschwader Stab.
Another old photograph from the period might have looked like this.
Although the plane's identifying letter is not shown under the wings, I did add it to the template, which is
here.