The other commenter is correct, this is a calligraphy pen.

The parallel plates of the nib are flat in cross section which isn’t very clear in the picture I took, which had the pen just oriented randomly. Maybe I should re-take it with the flat side towards the camera.

The Parallel takes the normal fountain pen nib design with the split down the middle and kind of flips it on its head. The ink flows between the two plates and because of this you get very even coverage. The Parallel is capable of, if you keep up your end of the operation anyway, producing really sharp, very square, and highly directionally differential lines. Even moreso than a traditional fountain pen. It’s also not as prone to having its ink dry out over short periods of disuse, at least in my experience.

Of course you can get them in an array of nib widths and of course I have all of the OG sizes. A 3.0 and 4.5mm nib were released later after I collected my whole set and one of these days I’ll get them, too.

They’re mostly used for calligraphy.