Pass Card

In Fallout 3, s 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.

Notes:
The blue and red pass cards may be a reference to the game Doom and serve no purpose so far.