The filigree decoration on the obverse like the engraved or niello silver plates on the reverse are gilded with amalgam. Known since Antiquity, this so-called amalgam gilding technique (or mercury gilding) makes it possible to gild, as evenly as possible, any metal (except lead and tin) using an amalgam of gold powder and mercury, the only metal that is liquid at room temperature and has the property of mixing with gold. The amalgam is applied to the object then heated over a charcoal fire (without smoke): the evaporation of the mercury - very dangerous - thus revealing the gold.
P