Hopje brown ink made by P.W. Akkerman pen store in The Hague.

Originally made to celebrate their 100th anniversary, this ink comes in a vintage-style bottle with a narrow neck with a marble stopper, to create a well at the top to aid in filling pens.

Hopjes are a type of Dutch sweets, with a slight coffee and caramel flavor, that originated in the 18th century. (Source: Wikipedia) Ackerman