Bob,
I keep a computer file of horn workers makers marks, currently with about 40 to 50 "marks" in it. I searched it and did not find a D. Beerman.
If you have a horn with his mark on it, I would appreciate a picture of the horn and the mark with what you know about him/her for my file.
My file also contains a number of marks of unknown makers.
I would welcome this same information on other makers marks from any members of the site who read this post.
John