In the distribution of electronic documents within an organization or across the perimeter of the organization, security is an important issue as the documents may be sensitive to a larger and a smaller degree. The filaments initially comprise Ca andor Sr andor Ba metal or alloy and then may be reacted with the Al matrix to form a strengthening intermetallic compound comprising Al and Ca andor Sr andor Ba. The first and second tracks have two resonant frequencies that are offset from one another from track to track within the first filter element such that they define a common passband by virtue of a lower-frequency resonance of the first track being in phase at the same frequency as a higher-frequency resonance of the second track. The clip module includes a body, a fastener, and a pressing structure.