(a) Penalty mail is restricted to articles not in excess of the weight and size prescribed for that class of mail receiving high priority in handling and delivery, except-
(1) stamped paper and supplies sold or used by the Postal Service; and
(2) books and documents published or circulated by order of Congress when mailed by the Superintendent of Documents.
(b) A penalty mail article which is-
(1) over 4 pounds in weight;
(2) not in excess of the weight and size prescribed for mail matter; and
(3) otherwise mailable;
is mailable at rates for that class of mail entitled to the lowest priority in handling and delivery, even though it may include written matter and may be sealed.
(
Section effective July 1, 1971, pursuant to Resolution No. 71–9 of the Board of Governors. See section 15(a) of