Sorry, I forgot to mention how I got that "used look"
The dark parts on the bow is not cambrium, there is no cambrium left on the bowback.
I stained the hazel realy dark and after the stain layer was dry, I used aceton ( might be den. alcohol)
to " clean" the bow from the stain a bit , after that I lightly sanded the wood and put a layer of clear varnish on it to get that kind of look.
Thanks, acker