Denny, that brush holder would never cause the armature to spin "backwards". No way to get it "wrong". When a D.C. motor works the field(case) magnets "pull/push' the armature towards the opposite N/S poll. With a set of angled brush holders(like a starter motor) the angle sets the direction and maximizes the torque. Put them in offset the opposite angle, and the armature gets "push/pulled" the opposite direction. Lots of small D.C. motors use the angled brush holders just to increase the "starting" torque.
