Wenonah Military Ads in 1917 follow a baseball theme

The first image seems to have the shape of the baseball diamond.

The second image from a 1917 "The Literary Digest" magazine, is home plate, isn't it?

Did they use different PO Box numbers to track the number of replies to the ads?
A quick check confirms the conjecture. In a 1917 copy of the "The American Magazine" the home plate ad uses PO Box 437. The same ad in McClure's Magazine uses Box 407. Still using that ad in 1920 in Cosmopolitan, Box 401 was used.