Related Clues:

• Bus. letter extra
• SASE, perhaps
• Ltr. extras
• Business letter abbreviation
• SASEs, e.g.
• Envelope contents: Abbr.
• Env. insertion
• Extra things in the env.
• Bus. letter attachment
• Collier's work: Abbr.
• Ltr. accompanier
• Ref. set
• 5 Placed inside: abbr.
• Check inside?: Abbr.
• SASE, for example