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 a 1 in 80 percent chance 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 cards seem to have no purpose. (they are not accepted by Protectrons in lieu of metro tickets!)