Sec.  1.337   Return of service.

   (a) If service of the subpena is made by a person other than a United States
   marshal or his deputy such person shall make affidavit thereof, stating the
   date, time, and manner of service.

   (b) In case of failure to make service, the reasons for the failure shall be
   stated on the original subpena by the person who attempted to make service.

   (c) The original subpena, bearing or accompanied by the required return
   affidavit or statement, shall be returned forthwith to the Secretary of the
   Commission or, if so directed on the subpena, to the official before whom
   the person named in the subpena is required to appear.