Zinc disc. These are really nice circular discs which can be used for engraving talismans onto, engraving spirit seals, or other similar designs. Thiese are very useful for when you wish to create your own magical items. I recommend first practicing on some scrap metal before using the perfect looking disc though. Brass is most often used for mercury (since mercury isn't safe to work with at all), Presidents of the Goetia, or Mercury pentacles for the Greater Key of Solomon talismans.