Bovril : "It's not the cowl that makes the monk" but Bovril makes the man : made from prime fresh ox beef / Bovril Limited.
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
The interactive 'hold up to the light' novelty guarantees the leaflet will be handled, looked at closely, and likely shown to others, amplifying the brand's core message of vitality.
Steal this when
You need a physical mailer or handout to go viral by incorporating a clever mechanical or optical trick that rewards interaction.