This is a slip ad from a magazine for military slips. Kayser produced slips for multiple branches in WWII. The woman shown in the photograph is not a WAC, but more likely a Nurse or other branch.
This typewriter, manufactured by L.C. Smith and Corona, is a standard 3C series made for the U.S. Army to be used in the field desks. Some were marked "U.S. Army" on the front, although this particular one was not.