[Mitchell]

But isn't it the 'milling' operation that is so critical to the use of anthrax spores as a dispersible weapon like the ones used? And that milling operation both leaves a signature of its methods and is very guarded info?

There are said to be weaponization processes that do not involve milling. However, I believe you are correct in focusing on the weaponization process, whether it involves milling or something else. The catch is that it would seem that the "weaponization signature" on the mailed anthrax may not match any known technique.

[Shermy]

Ping for old story you might have missed.