I was told when I bought the brush that it was an original prop from The Nightmare Before Christmas. That it was in fact used in the scene were the vampires are painting bullet holes on the duck. However, with closer examination of the film, this particular brush isn't seen on screen, nor is the paint color the same. The brush did come with a signed sheet of paper from Jerome Ranft (as it was supposed to have been a sale from his personal collection) stating it was made for that particular scene.
So, to give benefit of the doubt, I believe that it is a pre-production brush, made as a concept to determine either the scale, style, or color (perhaps all three) of the final look.
When I first picked up the brush I had never heard of Mr. Ranft. However, since watching Coraline, I am now very familar with him and his contributions to animation. Now I have something in my collection that ties both Nightmare and Coraline!