D.C. Code § 2-703
Envelopes or other materials which are used to enclose official mail shall bear upon its facing, in addition to the name and address of the agency mailing the official mail, the words “official business.”
Apr. 7, 1977, D.C. Law 1-118, § 4, 23 DCR 8746
1973 Ed., § 1-1703.
1981 Ed., § 1-1703.
This section is referenced in § 2-704.