I have an XRD 8 from the new Sturmey Archer. On the left, drum brake side, there is a cone, then a spacer, then a locknut. The spacer also retains the brake drum cover.
The cone is about 16mm in diameter and has a 12mm protrusion at its center with flats to prevent rotation. The protrusion sticks through the drum brake side cover. A spacer goes on the outside of the drum cover around the axle which has a recess with flats corresponding to the protrusion on the cone. The spacer also has slots on its outside so you could keep it from rotating with a hook spanner. Then there is a locknut which tightens down on the spacer.
I find it strange that the recess in the spacer is deep enough that its only contact with the cone is to keep the cone from rotating. The locknut tightens against the spacer which bears on the aluminum drum cover which bears on the cone.
Perhaps they left something about a millimeter too short or too long? I would think you'd want the steel spacer to be the only go-between between locknut and cone, and the drum cover should float on the axle. I am afraid the drum cover will crack if I use it as a spacer between cone and locknut.
According to the site I didn't leave anything out, but they didn't show if maybe someone left a cut out or left a part too deep or shallow.