No nut . . . just make sure the brake shoe adjustment is backed off via the slot in the bottom of the backing plate on the back side below the axle.
Once it is backed off - beat the living day lights out of the drum to break the rusty bond between the axle hub and the brake drum centering hole. I have a couple of big screw drivers that I work into the gap between the backing plate and the drum and then beat with a big hammer on the drum itself - alternating between the sheet metal between the studs and the perimeter of the drum.
Once the rust bond is broken at the axle hub location just inside the wheel stud circle, it will come right off. This is one of those jobs that it doesn't pay to pussy foot around. Think of your least favorite %&*$#@%!! and it will pop right off after a few satisfying blows. :p
