Sec.  42.4   Index of records.

   Each carrier shall maintain at its operating company headquarters a master
   index of records. The master index shall identify the records retained, the
   related  retention  period,  and  the  locations where the records are
   maintained. The master index shall be subject to review by Commission staff
   and the Commission shall reserve the right to add records, or lengthen
   retention periods upon finding that retention periods may be insufficient
   for its regulatory purposes. When any records are lost or destroyed before
   expiration  of  the  retention period set forth in the master index, a
   certified  statement  shall  be  added to the master index, as soon as
   practicable, listing, as far as may be determined, the records lost or
   destroyed  and  describing  the circumstances of the premature loss or
   destruction. At each office of the carrier where records are kept or stored,
   the carrier shall arrange, file, and currently index the records on site so
   that they may be readily identified and made available to representatives of
   the Commission.