Part of the problem is that Saddam had stocks of Mustard gas left over from the first persian gulf war (Iran v Iraq) but no sarin which is a nerve gas , rather than a blistering agent.
Its not really a weapon of mass destruction , its a weapon of mass casualty , but for the purposes of propaganda , it was labeled as such. It was originally meant to procede via artillery bombardment , offensives in WW1 and had to be delivered via Tons of gas , just to get the casualties that it did achieve.
Before WW2, it was used in Ethiopia by Italian forces and was requested by the British forces in Iraq , during that uprising .
Because of his experience in WW1 , and the fact that air power could deliver vast quantitys to the German hinterlands , Hitler refrained from using any sort of Gas or nerve agent , on Allied formations , largely keeping the program going via zyclon b , on the Jewish and undesirables.
Its last real appeal , was for the eventual soviet invasion of western europe , which never came off , the NBC agents were to be used in bombardments via IRBMS and bombers , for paralysing all major capitals ,and staging areas for follow on troops that would be deploying from Canada and the States.
All artillery and especially special munitions will have batch lots stenciled onto the shell, so as to determine the shelf life of a particular shell. My own guess is that the particular shell , was as mentioned binary ,which would have a different design , than say a 155 HE or Ap or AT round. The diameter would allow the shell to fit into the breech of a howitzer , but may be lighter or heavier depending on the munition involved.
The Binary method , was to have two separate chambers that would rupture and mix , allowing the cocktail to brew.
Declan