|There is more information available on this subject at Identification Badge on the English Wikipedia.|
Identification Badges, (or I.D. Badge for short), are small hand-size cards for personnel identification. They are used for security reasons, jobs, etc.
Locating the Badges
These badges can be found in many places throughout Halo 3: ODST in both Firefight and Campaign. Such as on the firefight level Security Zone there are two badges that can be located near the spawn point on the table in that room behind you.
Four ID Badges can be found on the floor of the bottom level of the building you start in the firefight mission "Rally Point" among the litter, there is another ID Badge on the level Data Hive when you come into the white room, just after you find Veronica Dare, with vents on the wall behind the door, once you go in go to the vent on the right and there will be a badge stuck to the grate. Those four badges on Rally point can also be found during the campaign in the same place.