Thank you 25thapril for the 87mm dia of the SBML 4.2" Mortar Smoke BE. If you have not got the discarding sabot, which would make the dia about 105mm, the bomb, is incomplete. I knew that the bourellet on the 3" bomb for use with the 4.2" BEDS was cast larger than the other 3" bombs, to prevent the sabot, which fitted over it, from leaving the bomb behind on firing. The actual outside diameter tolerances, of the two identical sabot half rings, is given as between 2.082 and 2.084 inches.
There was a thread a while back, where I and others gave what information we could, to enable someone to make reproduction sabots. I believe it may have been in the US.