The weekly comic strip copyright book sent to the Copyright Office, New York City-area newsstands, and some subscribers reprinting the original proof sheets of the upcoming week's worth of comic strips. Meant to be used to help in securing copyright of the strips.
Title of the comic had an exclamation mark with it in the 1980s, but it seems to be just a part of the graphic design (as the title was in a word balloon) and not really a change in the publication's title.
Start year of 1939 confirmed in the submission to the U.S. Copyright Office recorded in the Catalog of Copyright Entries, Part 2, Periodicals, 1941, New Series, Volume 36, Number 3.