VERY well put. I do believe you're probably right.
http://www.washingtonpost.com/wp-dyn/articles/A47864-2001Oct24.html
"The ongoing USAMRIID studies on the spores used in the U.S. attacks involve examinations using conventional microscopes and scanning electron microscopes, along with complex chemical analyses that are difficult to conduct even when the bacteria in question are not dangerous. [sentence omitted]
Results of those tests have not been made public beyond a simple description of how small the spore particles were in the Daschle letter. That particle size, 1 1/2 to 3 microns in diameter, said Sen. Bill Frist (R-Tenn.), is extremely small -- a first requirement for making "weapons grade" anthrax spores for warfare or terrorism."
The usual way anthrax spores are created is to first create a "wet" anthrax culture and then dry it (taking the lid off the jar is one way). The dehydration will cause the anthrax to form spores. But just how the spores are dried is critical to other matters, so drying them in the proper fashion is not easy.
Among other things, anthrax spores come in a great variety of sizes, but only spores of about one to five microns in diameter can cause pulmonary anthrax. The spores must be under five microns in size to be inhaled deep enough into the lungs to be infectious, but more than a micron across so they will adhere to the lungs.
Side note: anthrax spores of sizes under one micron and over five microns can cause cutaneous and intestinal anthrax. They just won't cause pulmonary anthrax.
What type of drying method is used to create anthrax spores from wet cultures can determine the "yield" of spores of the desired diameters, and how easy it is to treat them so the spores won't clump together in groups in excess of five microns in diameter.
These drying methods are one means of determining the country which created the spores, though that means is not exclusive. It is possible to create small amounts of spores with, for a given country, non-standard (relative to the most common method aka "production standard) drying methods, at greater expense, for experimentation and deception purposes.
And post-spore production techniques are commonly used to increase the number of spores of the desired diameters. Milling is a common method, but the milling methods are reputedly not something which can be done effectively without use of rare and expensive machines operated by skilled personnel. Improper milling can reputedly make the spores some to almost totally harmless, and certainly make them impossible to keep them from clumping together.
Getting back to the Post article:
"In the United States, that problem was solved by Bill Patrick, who developed the process at Fort Detrick as part of the U.S. biological weapons program that ended in 1969. The process is protected by at least five secret patents held by Patrick. It involved freeze drying and chemical processing and was achieved without having to grow vast quantities of spores or mill them to terribly small dimensions, Patrick and other experts said.
... [paragraph omitted]
The Russian program, which has been described in detail by Ken Alibek, who ran it for many years before moving to the United States to do biological research, required the production of much larger quantities of spores that were more heavily milled than the U.S. spores and used a different kind of freezing and coating process.
The Iraqi technique, uncovered by U.N. inspectors, was a novel one-step process that involved drying spores in the presence of aluminum-based clays or silica powders, said Richard Spertzel, who was part of the U.N. Special Commission (UNSCOM) team that was to uncover and destroy Iraq's weapons of mass destruction program after the Gulf War. [sentence omitted]
"If [U.S. investigators] can get a clue as to how the material in the Daschle letter was prepared, that might narrow the field," Spertzel said. "It may not pinpoint it, but it may narrow it."
I recall an earlier news story, whose URL someone posted a while ago on the Freep, where Spertzel said the Iraqi method of preparing the spores created a characteristic crystallization pattern which could be identified under a microscope.
Summary: creation of anthrax powders which can cause pulmonary anthrax entails roughly the following steps (note that these are broken into arbitrary steps - as a practical matter they overlap some to a lot depending on the methods used):
1) Create "wet" anthrax cultures;
2) Make dry spores of the culture;
3) Treat the spores so as many as possible will be of the right size;
4) Turn the spores into powder;
5) Treat the spores so they won't clump together.
BINGO!!!!!!
You're so smart!! Glad to see someone here has the half a brain I'm missing.