As you heard in our last post, you could, in 1938, send away to Dr. Caldwell to get a copy of a "Monticello Party Line" cookbook and a sample bottle of Syrup Pepsin.
Unfortunately, I haven't been able to locate a copy of the cookbook given away in the 1938 season of "Monticello Party Line", but have located two others from 1936 and 1937. In this post, "Sara and Aggie's Party Line Cookbook", the Second Edition, offered as a premium on the show in 1936. In the booklet, you'll find recipes, household hints, pictures of the cast and the show and, of course, some good words about Syrup Pepsin.
Of course, some staff at an advertising agency put the thing together, but they try to maintain the illusion that it was written by Sara and Aggie themselves.
It was a much simpler time in advertising.
The PDF is 7 MB and runs 17 pages. It also includes, at the end of the file, a letter from Sara and Aggie that was enclosed with the recipe book and Syrup Pepsin sample.