My guess is that it was made by the Indiana Band Inst. Co. after the Martin buyout. I have a 1933 Indian head one (Indiana) an dit looks similar but with the opposing bell keys and front alt. Eb. I would put it in the 1935-42 period. If the bell rings are fluted like the old Pontiac hood stripes, that would confirm this. I cannot tell in the photos. Many stencils thought to be from Martin were actually Indianas or Courturiers.