In the review of the Amerithrax Letters mailed in Princeton, NJ at a mailbox on Nassau St., with the information inside of the letters decrypted at AmerithraxLettersDecoded, you find that there is one of the two that featured a series of handwritten letters that are heavily etched with a double/triple-scored pen stroke.
When you connect all of them together into a Path Cipher, you find they draw out a familiar Z shape.
Likewise the investigations from the media also took notice of these styled additions to the letter, and in their search for the suspect they coined him – “Mr. Z”
“”Mr. Z” was a pseudonym used by columnist Nicholas Kristof in 2002 to describe a suspect…..The columns suggested “Mr. Z” may have been involved in the anthrax attacks or previous hoax letters.”
https://www.theatlantic.com/magazine/archive/2010/05/the-wrong-man/308019/
The Z-shaped image is coined from the Bates Letters signature…..it is identical in every way.
Another mainstream media PBS investigative report that nails down the same theories in detail.
https://www.pbs.org/wgbh/frontline/documentary/anthrax-files/
The archived information about the files from the Amerithrax Investigation
https://documents.theblackvault.com/documents/terrorism/amerithrax/847572.pdf
The information from inside of the Amerithrax Letters and also from the later Fallen Angel Ricin Letters revealed the name of the suspect, calling himself by his stage name – CYPHER ZERO – aka Michael Aaron Woldow
You can find his information included in the linked page of the worksheets in the ciphers added above.