I am surprised I had never come across this before!
For a fountain pen aficionado like me, I was intrigued that I was not aware of the existence of these things. I have used dip pens in the past – you know with nibs in the end and usually a holder or a quill at the other end. But these are very different kinds of dip ink pen.
First, they are made of all glass. Second, the nibs are not flat. They are all cylindrical or bulbous! I was wondering how the ink would flow. (Usual nibs have that slit between the tines that has the ink flowing due to capillary force). Turns out the ‘nib’ has intricate shallow trench like etchings that wrap around like the threads in a screw. The ink, when dipped in, is held in those “trenches” and slowly flows out.
Fairly unique! Got a few delivered from China. Was never aware of this. Were you? Wrote the first letter to my niece using this!