Sec.  1.258   Closing of the hearing.

   The record of hearing shall be closed by an announcement to that effect at
   the hearing by the presiding officer when the taking of testimony has been
   concluded. In the discretion of the presiding officer, the record may be
   closed as of a future specified date in order to permit the admission into
   the  record  of  exhibits to be prepared: Provided, The parties to the
   proceeding  stipulate on the record that they waive the opportunity to
   cross-examine or present evidence with respect to such exhibits. The record
   in any hearing which has been adjourned may not be closed by such officer
   prior to the day on which the hearing is to resume, except upon 10 days'
   notice to all parties to the proceeding.