If you purchase a brand new Asian Mah Jongg set, chances are that the enclosed rules are a reprint of a 90-year-old Chinese original. For real variation in instruction manuals the US and Europe of the twenties offer a lot more choice.
In China a plain cover was considered enough. Western toy makers however made the most of it. With all kinds of booklets, folders and leaflets. Often well written and informative. And, especially when a renowned brand was involved, with its own and distinctive branding.

NB. Printing dates are not always reliable since rule books were often added later.