Akkerman Blue fountain pen ink made by P.W. Akkerman pen store in The Hague.
Akkerman Blue is a step deeper in color than the Residence Blue (#2). It has amazingly beautiful shading properties and a rich medium blue tone.
Originally made to celebrate their 100th anniversary, this ink comes in a vintage-style 60mL glass bottle with a narrow neck and a marble stopper that creates a well at the top to aid in filling pens, allowing you to get every last drop of ink from the bottle.