I incorrectly labelled the right hand tail unit as a Streamlined bomb tail but with two cut-outs it will be from a bomb filled with Chemical, or Smoke, or Practice Inert.Interesting thread. The 4.2 inch bombs I find are generally in one (body ruptured) or two (top half ripped from lower half) pieces. Those I find have the hexagon nut below the body, as explained by US-Subs. usually the tail unit is still attached.