A properly marked source document contain some secret information?

A properly marked source document containing secret information should include clear designations indicating its confidentiality level, such as "Confidential," "Secret," or "Top Secret." It may also feature specific handling instructions, access restrictions, and a date of classification. Additionally, such documents often include a warning or disclaimer about unauthorized disclosure. These markings help ensure that individuals handling the document understand the sensitivity of its contents and the necessary precautions to take.