Printers' Ink, Apr 25, 1912 (Vol. 79, No. 4): address before the Sphinx Club by Charles R. Wiers of Larkin Co.
The pattern
This still is filed under House ad as portfolio.
Define
The firm advertises itself by showing the work, not by describing the work.
Mechanism
Proof by exhibit. The portfolio is the claim. Captions stay short. The pieces carry the argument.
Verdict
We sell craft and the buyer can judge from examples.
Why it works
It uses a strong, relatable analogy (doctor prescribing medicine vs. agency prescribing media) to position the agency as a necessary expert rather than just a vendor. It elevates the role of the advertising agency to that of a professional consultant.
Steal this when
You need to justify the value of your consulting or advisory services to a client who might think they can just choose the tools or mediums themselves.