Section 30(1)(e) in The Indian Post Office Rules, 1933
(e)Every copy or bundle of copies of the newspaper shall be posted without a wrapper or with a wrapper open at both one which can be easily removed for an inspection at the newspaper or in an unfastened envelope, provided that whatever means are employed to secure copies of the newspapers while in course of transmission by post, the registration marks referred to in clause (c) must be clearly visible without removing the wrapper or envelope.