Examining the evolution of the "Good Housekeeping" Seal of Approval--one of the first codes to set standards for the products advertised in a periodical, a study analyzed issues of "Good Housekeeping" magazine from 1909 to 1975 (with the exception of issues from July 1929 to December 1938). The study also examined elements that may have been related to the evolution of the seal, such as relevant legislation, changing advertising practices, and an increasing consumer sophistication. Analysis revealed that in every issue, usually at the beginning of the magazine, the "Guaranty to Our Consumers" is printed. Before 1941, the seal was found only in conjunction with articles from the "Good Housekeeping" Institute. After examining the issues, a total of 25 changes were found in the Seal of Approval (wording, graphics, presence) and in the wording of the guaranty. Factors which may have influenced these changes included: (1) World War I (from December 1913 to August 1915 there was no advertising on the inside of "Good Housekeeping" and no Index to Advertisers or "Our Guaranty"); (2) a changing atmosphere for advertising as internal attempts at advertising regulation became the norm instead of the exception; and (3) major changes in format as the magazine increased in both size and length. (A chronology of the "Good Housekeeping" Seal of Approval and three figures are included; three pages of footnotes are appended.) (MM)