My commission stamp. I ask if artists will sign their work, put their own stamps etc, but i can't force them too. I can make the stamp for me a requirement for finished product, which I do. Too many art thieves and dump sites that don't give credit back to the artist. If the artist isn't recognizable by my stamp is, they can contact me and I'll point them at the galleries of the artist who did the work. Unless the artist asked to be anonymous.