After further review, and thought, I am pretty certain that 4117/17 was a DIII. According to the Data file on the DIII production of the DIIIa started @ 4189/17. I also recall looking into this Myself now. If I recall correctly the text in the Pfalz aces book mentioned Heldman flying DIII D4117/17 and the Profile said DIIIa. I now recall asking about this Myself either here or on the Drome and the answer was DIII. I hope this helps.
RAGIII