Is there some reason you included me in your post?
You were asking what "usable" meant, ie the question as to if the shells were in usable condition. If they were binary sarin shells like the one used in the IED in 2004 the answer is that they are usable, binary means the sarin components are stored separately in the shell and do not mix until it is used. This greatly increases the "shelf life" of sarin shells. Mixed sarin degrades, binary sarin apparently does not. This is a huge detail IMO and one that neuters the "old degraded" argument.