Charles Atlas 'Dynamic Tension' ad, Weird Tales September 1941
The pattern
This still is filed under If-then promise.
Define
A conditional contract: if you do this, you get that. The sentence can be tested against the reader's own case.
Mechanism
Specificity does the persuading. The if names the action. The then names the outcome. Hedging kills it.
Verdict
We can name both the action and the result without adjectives
Why it works
The headline makes the coupon the hero rather than the course, so the small act being asked for is the same act the proof story is about. Reproducing O'Brien's actual mailed coupon beside the blank one collapses the gap between the reader and the success case: the arrow says do this, here is what it did. The offer is a free book, not a course, which lets a self-conscious reader respond without admitting he is buying anything. The risk reversal, "there's no cost if I fail", and the fixed fifteen-minute daily price both shrink the perceived commitment before the coupon is ever reached.
Steal this when
Use this when your funnel starts with a small free step and you have one named customer who took exactly that step and got a visible result. Show the artefact they submitted next to the blank one you want filled in.