Brotherhood registration

The Brotherhood registration is an alphanumeric code identifier unique to each member of the Brotherhood of Steel.

Structure
Every number is structured as follows:

XX-YYYZZ


 * XX are two capital letters representing a member's last name (or chosen name). The usual rule is that the first two consonants are selected (Maxson returns MX).
 * YYY is the serial number. Elder Arthur Maxson has the lowest number as the Supreme Commander, 001.
 * ZZ is the rank of the holder, updated as they advance through the ranks. Depending on the rank, it may be a single letter or two.