TWSBI Eco Fountain Pen - Serpentine with Bronze Trim and NibA serpentine green with quiet visual depth The TWSBI Eco Serpentine is a limited edition piston filler with a mixed resin finish inspired by the tones of serpentine stone. The blend of greens and browns varies slightly between pens, so no two are exactly identical. Bronze trim adds a warmer contrast to a design that otherwise stays very functional and familiar within the Eco range. What sets it apart High capacity piston filling system, for long