VERIFIED SOLUTION i

How to understand the conversion of a street address to a PO box address when running in CASS mode in GeoStan

Product Feature: General
Dual Address Match Logic indicates how to handle addresses with multiple non-blank address lines.

The Domestic Mail Manual states to match to a PO Box first.

If the box information is included after the street address then it is not used in the match and is simply kept as superfluous information (which is why the Box became an #).

If the box in question is a private mail box, then an accepted private mail box indicator should be used to bring back that information.

PMB is the Standard Private Mailbox Designator and # is the Nonstandard Private Mailbox Designator. 
UPDATED:  November 20, 2017