M071 describes standard markings for attachments or enclosures for First-Class Mail, Periodicals, and Standard Mail.
First-Class attachments must be marked First-Class or Letter Enclosed. Standard Mail attachments must be marked Standard or STD.
When a Periodicals publication is mailed with a nonincidental First-Class Mail or any Standard Mail enclosure, the corresponding First-Class Mail Enclosed or Standard Mail Enclosed marking must be placed on or in the host publication as follows:
a. If placed on the outer wrapper, polybag, envelope, or cover of the host Periodicals publication, the marking must be set in type no smaller than any used in the change-of-address notice in the identification statement.
b. If placed in the identification statement, the marking must meet the standard in 1.2a.
c. Except under P070, the marking must not be on or in copies without a First-Class Mail or Standard Mail enclosure.
The mailer must mark First-Class Mail Enclosed or Standard Mail Enclosed on each Standard Mail and Package Services parcel with such an enclosure. The marking must be placed below the postage and above the delivery address, using any method that produces legible wording.
DMM Issue 58 (8-10-03)