The Flags are an Item in Secret files 3. They have his first Appearance in the Mission „Max Grubers House “.
You'll find them in the Book from Max Gruber. When you have them, you've to go to map from australia, which is in his bedroom. You've to put them in the follow four cities: Adelaide, Brisbane, Broome and Hobart.
When you have done this, a secret shelf opens. Inside are the Keys for the Museum in Berlin.