Items Treated As Classified
(From the NSA Handbook)

For purposes of transportation, storage and destruction, there are certain types of items which must be treated as classified even though they may not contain classified information. Such items include carbon paper, vu-graphs, punched machine processing cards, punched paper tape, magnetic tape, computer floppy disks, film, and used typewriter ribbons. This special treatment is necessary since a visual examination does not readily reveal whether the items contain classified information.