What is the purpose and history of the FAA's tracking system for handbooks and manuals?
I must have too much time on my hands, because I actually looked this up in the handbook on handbooks that aeroalias referenced.


  5.1.2.3 Document identifiers
  
  The identifier for handbooks shall be placed in the upper right corner
  of the first page. The identifier as assigned by ATO-W Enterprise CM
  shall include the letters “FAA” followed by a hyphen, then any
  combination of numbers, letters, or dashes. It shall not include any
  other symbols.
  
  5.1.2.7 Handbook numbering.
  
  FAA handbooks are assigned traceability numbers by Enterprise
  Configuration Management organization following endorsement by the
  Systems Engineering organization. This alphanumeric designator will
  utilize the following format: FAA- HDBK-(XXX), where "XXX" equals a
  three digit number. The handbook number is placed in the uppermost
  right corner of the cover page.


Section 5.1.2.5.1 Superseding revisions doesn’t appear to be followed in any of the FAA handbooks I have.