Claimants have the right to be represented before the Board at all stages of the proceeding by an attorney at law duly licensed to practice in the State. The attorney shall file a notice of appearance and, when appropriate, a notice of substitution, before or at his first appearance. If any party designates an attorney at law to represent him and the attorney has executed and filed with the Board a notice of appearance in the matter, in substantially the form annexed here, the notice shall remain in effect until: The party represented files with the Board a written revocation of the attorney's authority; The attorney files with the Board a written statement of his withdrawal from the case; The attorney states on the record at a Board hearing that he is withdrawing from the case; or The Board receives notice of the attorney's death or disqualification. After a filing of a notice of appearance in accordance with this regulation, and as long as the notice remains in effect, copies of all written communications or notices in the matter to the party shall be sent to the attorney rather than the party represented, or to both the party and his attorney. Service upon the attorney shall be deemed service on the party he represents.