In the latest edition of "Old Bike Australasia" there is a picture of a Series B Black Shadow being raced (nothing peculiar there). BUT if one looks closely, both front brake arms are reversed! They are pointing backwards!
A thing to consider here is the "self servo" effect. The theory being that, with the arms facing forwards, any slight movement of the back plate in the direction of wheel rotation increases the amount of pressure that the rider is applying via the handle bar control. This can give a grabby brake performance, and in extreme conditions can cause the brake to lock and any failure of the torque reaction arrangements results in the brake being "winched "on by it's own cables, even when the handle bar lever has been released. That is the theory anyway. (dont ask how I know this, I still have the scars that prove the theory)
John