47 CFR § 1.338 - Subpena forms.
(a) Subpena forms are available on the Commission's internet site, www.fcc.gov, as FCC Form 766. These forms are to be completed and submitted with any request for issuance of a subpena.
(b) If the request for issuance of a subpena is granted, the “Original” and “Duplicate” copies of the subpena are returned to the person who submitted the request. The “Triplicate” copy is retained for the Commission's files.
(c) The “Original” copy of the subpena includes a form for proof of service. This form is to be executed by the person who effects service and returned by him 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.
(d) The “Duplicate” copy of the subpena shall be served upon the person named therein and retained by him. This copy should be presented in support of any claim for witness fees or mileage allowances for testimony on behalf of the Commission.