Burdock blood bitters : plain as daylight.
The pattern
This still is filed under Keepable trade card.
Define
A small card people keep (pretty, useful, or collectible) that carries the brand after the encounter.
Mechanism
Retention object. The gift is the media. Recall is paid for by usefulness or delight, not by repetition.
Verdict
We can put a physical or digital keepable in someone's pocket and they will not throw it away.
Why it works
It uses the classic 'us vs. them' positioning by attacking other quack medicines to establish its own honesty. The aggressive denunciation of deceit makes their own testimonials appear more credible.
Steal this when
Selling in a market full of scams or low-quality competitors, where you need to loudly differentiate your honesty.