Golden tablets with the seal of the ruler that issued the pass and the seal and name of who it was issued to. About the size of your palm of solid intricately etched gold. The holder of the tablet is backed by the authority of the king to make any required purchases on credit or enter any place they deem necessary. A very powerful token indeed.
There is a land far to the east that is a great, desolate, near-empty wasteland home only to barbarians, ghosts and monsters. Many nations launche expeditions to this land, seeking to find the rumored-at treasures and riches beyond it's outer fringe.