Pancho Villa and henchman poster

This poster has been un my possession for at least 20 years. It was bought from a widow at an estate sale . She had no idea what she was selling and my mother had no idea what she was buying. The paper is extremely brittle. The date appears to be stamped. I am trying to determine whether it is genuine. The only real question that I have is the size. It is approximately 8"by 11. The paper will flake off if touched