Nine digit code used by the Unabomber
in his correspondence with the media
and law enforcement
. Such codes are typically used by criminals and terrorists
so the authenticity of their messages can be verified. The code is kept secret from the public, of course.
This particular code is the social security number
of a petty criminal
. That man has a tattoo
that says "pure wood
". Probably a coincidence or a false trail planned by the Unabomber.