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.
MoonInk: This alchemical product has 101 uses. The Ink/Paint dries to be totally clear and almost unnoticable. Under moonlight, it comes forth as a silver ink. It was originally used by the Elventi to enhance certain pieces of art. It is used by espionage types to produce secret messages, nobles for hiddle plots, and diabolical cultists to write their spell books (usually in books of holy texts, to throw off people reading it).