Counterpoint,
'Either way, it looks like the OPCW was given some lab produced substance that had also probbaly served as a reference for Porton Down trying to identify its nature.'
Why would Porton Down need a 'reference substance'? You have heard of mass spectrometers, right? And chemical formulae?
'BTW - the fact that the substance analysed by OPCW was found to be so 'pure' would rule out those speculations on mixing of binary agents.'
Why? They said 'high purity', not perfectly pure.
'Most unlikely that the military (or an assassin) would take steps to purify something to the degree found, and stated so, by the OPCW.'
A professional lab would not need to 'purify' a substance if it did not have impurities in it in the first place. Given the dangerous nature of the substance, I assume it is produced in a negative pressure environment.
I really doubt you are a chemist, Counterpoint (nor am I but I did study it up to university level). This is yet more FUD, isn't it?
The purity indicates that it was made in a professional lab (i.e a small factory) and not cooked up in someone's garage, that is all.