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.
Asclepius' flies are similar in size to the ordinary housefly, but they are white, with crimson eyes (ugly little creatures). Unlike most flies, however, they are not diseased, in fact their remarkable immune system contains agents which tackle even human illnesses. This is the source of their white colouring also. The standard technique for capturing them, to use their juices, is to tempt one onto the palm of one's hand and then to quickly wring your palms, then rub the mush onto the afflicted area. This is not for the squeamish, but has definite healing possibilities.