The quality of Confederate iron was especially bad after about 1862, leading to many casting flaws and bubbles in the iron. While the North had the luxury of rejecting these type flawed shells, the South used them anyway. The iron quality at the Tredegar Iron Works in Richmond was especially bad while the iron used at Selma was of a much better quality resulting in a better product. The brass sabot was added after the round was cast and the cuts in the sabot were to allow the sabot to expand slightly and grip the rifling of the gun better along with allowing the flame to reach the fuse. The raised ridge near the top of the shell is called a bourette and it helps steady the shell in the tube and enable it (in theory) to fly straighter. The triangular pieces at the bottom are the wooden fuse holders that would hold the paper fuses. These are 3" Broun shells which are usually found on late war battlefields.