During World War II the Office of Strategic Services (OSS) gathered and analyzed intelligence information, ran guerrilla campaigns, and conducted psychological warfare against Germany, Italy, and Japan. This is an example of an envelope to be placed in the German mail. The OSS addressed envelopes containing propaganda leaflets to individuals in Austria and Germany. The names and addresses were obtained through phone directories. Return addresses used the names of banks and export and import companies. These addresses made it plausible that large numbers of envelopes might be in one bag.
National Archives, Records of the Office of Strategic Services