Related Clues:

• RSVP card, e.g.
• Business letter letters
• Ltr. add-in
• Letter-ending abbr.
• In the env.
• Something in a ltr.
• Business-letter abbr.
• It may be a copy of a ck.
• Cover letter letters
• Afterthought No. 2
• Doc. with a ltr.
• Cover-letter letters
• Something inside an envelope: Abbr.
• Compton's, for one: Abbr.
• SASE, often