Define
A physical letter or pack whose only job is a measurable reply: an order, a donation, a call.
Mechanism
Response engineering. Outer, letter, lift, reply device. Every surface earns its keep or it is cut.
Verdict
We can mail, track, and fulfill, and the unit economics survive the stamp.
Don't
We want presence in a mailbox. That is branding. This pattern keeps score.
Rights-cleared examples
V - MAIL TO BE SURE" poster
Church and Sunday School Publicity: Practical Suggestions for Using the Printed Word
Direct Advertising and Sample Book of Mill-Brand Papers (1917 volume)
Hundred Point Sales Letters
Larkin Company Order Form (1914)
Raising Money
Standard Plan of Campaign: Every Member Canvass, Presbyterian Progressive Program
The Mailbag (1918 volume)
The Science of Marketing by Mail