Hello Frank -

The thing that struck me when I first saw the first 2 images of the envelops when they were released is that the writing slanted off to the bottom right - I think this happens if a right handed person is working from a stack of letters, moving them from his right side to the writing area and then to the left -

My assumption is that the letters and envelops are undergoing neutron activation analysis to determine point of manufacture, if they don't have manufacturers marks in either glue or paper

As near as I can make out from the confused reports, there seems to be 2 strains of anthrax, one inhalation, one cutaneous - I don't know which is tied to which envelops -

EP