(a) Method of service. Notices of hearing, decisions, orders and
other papers may be served personally or by registered or certified mail
or by telegraph. When service is by mail, the date of service shall be
the day when the matter served is deposited in the United States mail.
(b) Upon whom served. All papers, except as herein otherwise
provided, shall be served upon all counsel of record and upon parties
not represented by counsel or by their agents designated by them or by
law and upon the Assistant Secretary, or his designated officer, or
agent or Administrative Law Judge where appropriate. Service upon such
counsel or representative shall constitute service upon the party, but a
copy also shall be transmitted to the party.