Related Clues:

• MS. enclosure
• Motor oil can letters
• Encl. to an editor
• Collier's, for one: Abbr.
• Encl. with a manuscript
• In an env.
• Bus. letter extra
• Letters on a motor oil can
• SASE, perhaps
• Return env.
• Business letter abbreviation
• Oilcan letters
• Letters on an oil can
• Enclosure with a manuscript, for short
• It might accompany a MS.