PLK928663 Piston filler including a 24 carat gold plating and an elaborately striped body made of celluloid acetate. The nib of the Souveran piston filler M800 is made of 18 carat/750 gold, the nibs of the models M600 and M400 are made 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 model M800.