[1] In an astrolabe, a tympan is a metal plate on which the coordinates of the celestial sphere (azimuth and altitude) are engraved in a stereographic projection.
[1] The Bruzer's Tympan is a sheet of oiled manilla paper which was securely fastened to the face of the platen of a letterpress printing machine.
Underneath the tympan would be a packing which would vary in grade of firmness relevant to the type or image to be printed.
Pre-cut tympan papers were relatively expensive and, as such, were reused depending on their condition and the nature of the work.
The under packing consisted of loose fibre paper/board (sometimes known as saffron) which absorbed the impact of the letterpress principle thus avoiding damage to the hand-set or pre-cast typography or engravings.