Unfortunately thats the best pictures I have of the cockpit of a D.520. Another option for you would be to compare the pictures to other aircraft of French make and see if you can get a clearer picture if no one else can help. I will keep my eyes open though.
Your welcome Vespa2, I do have a few books on this aircraft. If you are looking for something else on the air body let me know and I will take a look and see what I can find.