20505 is a known CIA zip code and this letter was mailed to me by CIA, revealing I was under consideration for CIA employment before I started working. CIA is supposed to protect the future cover of CIA National Clandestine Service applicants during the recruitment process but the bureaucracy often fails to do so. My cover was also blown by CIA in October of 2009 (and continuously after by CIA staff) following my car accident and suspension from CIA employment.
DD1 refers to Dulles Discovery a CIA facility responsible for processing applicants. CIA applicants undergo Medical and Polygraph screening at the DD1 facility.