Chester,
The indicated washer spans the face of the backing plate with the lip facing outward. It gives a surface for the inboard end of the clutch springs to sit upon. the slight lip prevents the ends of the springs from working their way outward due to centrifugal force and possible binding in the holes where they pass through the flywheel.
There are probably some section views of the CW/SW clutch about. All the ones I have seem to be of the slightly later EW style. There are other pictures of CW/SW clutch components shown here on the Forum, but all fully disassembled, such as yours.
-Doug