From Hey Kids Comics
A. A. Wyn's Magazine Publishers was a publishing house established and owned by A. A. Wyn. It began in the 1930s as a pulp magazine publisher, and included titles such as Ace Mystery and Ace Sports. They also used the name "Periodical House", and also branched out to publishing comic books as Ace Comics. In the 1940s the company also began publishing books.
In 1952 Wyn founded Ace Books, and by the mid-fifties Wyn had sold most or all of his hardback rights, and may also have ceased publishing magazines by that time to focus on Ace Books.