The middle seat bottom appears to be the primary source for where the mice had been scavanging nesting material, as well as a source of a lot of the stink. You'll notice the orange, dusty rust on the top if the spring cage. This was removed just by wet buffing with a light phosphoric acid, then coated with zinc-phosphate to re-seal the surface. As you can see, the burlap was disintegrated, and the padding crushed down into the springs. The padding was a total loss.