I recently purchased a set of Nancy Drew Cameo book club materials at eBay. The set came with the book club's letter, a flyer/poster (double sided) on the club, and a mail in card.
What was really neat was the artwork on the reverse side of the Cameo flyer--which was not used in the books themselves--see image below:
The artwork shown was probably just for the advertising as it appears to be all one collage image with scenes from books 30-36
Books were priced at 1.49 each and The Clue of the Velvet Mask would be 10 cents as the introductory volume in the club.