The doctor's pocket remembrancer / J.C. Eno Ltd [1931]
The pattern
This still is filed under Utility premium.
Define
The free thing is kept because it works (a calendar, a tool, a template) and the brand rides along.
Mechanism
Usefulness as media. Frequency of use is frequency of exposure. Distinct from a keepable card: here the object has a job.
Verdict
We can give something people will actually use next week.
Why it works
It uses the reciprocity principle by giving doctors a genuinely useful, objective pocket diagnostic guide. The soft-sell pitch at the end feels respectful of the professional's intelligence.
Steal this when
You are marketing to professionals and want to build goodwill by providing a highly useful, non-promotional reference tool.