Pass Card

In Fallout 3, Pass Cards are items that are randomly encountered.

Locations
Pass cards are located in random places throughout the Capital Wasteland. They are dropped by ghouls or centaurs, and may also be found on trogs if The Pitt is installed.

A ghoul has 1 chance in 80 of dropping a pass card of either color, A centaur has a chance of about 1 in 170, & trogs have an even smaller chance of about 1 in 240.