Wikimedia commons entry, claiming it is froma citation to "Una Storia Segreta" by Lawrence Distasi. The licensing metadata from the picture claims that it is a "work prepared by an officer or employee of the United States Government as part of that person’s official duties".
Source (Replica sales website)
Were there World War II propaganda posters in the United States telling people not to speak German, Italian or Japanese, and to "Speak American"?