Piston filler including a 24 carat gold plating and an elaborately striped body made of celluloid acetate. The nibs of the Souveran piston filler M1000 and M800 are made of 18 carat/750 gold, the nibs of the models M600, M400 and M300 consist of 14 carat/585 gold. All nibs are refined with a rhodium decor and their writing qualities were tested by hand. The fountain pens are equipped with a differential piston-filling mechanism, of which is elaborated with high-value brazen components on the models M1000 and M800.