The faceplate is held on by the outer ring. There are also two steel straps that attach to each other and are used to hold the cover to the spare. They in turn are held to the wheel center with a locking hub cap. If you have the V-8 club' 35-36 book there are photos with a good description of how it all works.
www.earlyfordv8.org Use the left menu to go to the "on line store"