The cap reminds me of glass nibs I’ve seen.  I don’t see the artist’s inspiration noted in the article, but I wonder.

Dutch designer Rein van der Mast 3D prints bronze Pjotr fountain pen with an Ultimaker

Dutch designer Rein van der Mast (also known as Pjotr) is at it again with a new 3D printed fountain pen, but this time he’s taking the technology into his own hands. The exquisite writing instrument was printed with an Ultimaker using a bronze filament from ColorFabb, and posted just recently on van der Mast’s website.

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http://www.3ders.org/articles/20170910-dutch-designer-rein-van-der-mast-3d-prints-bronze-pjotr-fountain-pen-with-an-ultimaker.html