Printers' Ink, Sep 3, 1914 (Vol. 88, No. 10): "Organization of an Advertising Agency" by Earnest Elmo Calkins
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 acts as a 'meta-ad': an ad for an advertising agency showcasing their work for a client. By highlighting the client's success and leadership, the agency indirectly proves its own value.
Steal this when
You are a service provider (like an agency) and want to advertise your services by showcasing a successful client case study as the main focal point.