This is Pelikan's bottled ink for fountain pens, "Edelstein Ink Jade." It's a high-quality ink collection from Pelikan, a long-established German manufacturer. "Edelstein" means "gemstone" in German, and the ink colors are also derived from gemstones. This "Jade" is a vibrant green, like the gemstone jade. Thanks to a special ink recipe, it achieves an especially smooth writing feel. It has been used to some extent.