1) Notice the porosity on the tip surface: two kinds a large one (spherical) of the order of 20 microns (1/3 of a human hair diameter) and smaller one about 1 micron.
2) line marks: in the transverse on the top and at 45 close to the spherical pore. Could be either from grinding or from writing.
3) Is this the "baby bottom" effect?
4) Notice the rough surface in the side wall of the slit - from the cutting wheel.
5) the particle on the surface (lower and left from the big pore) is probably dust.
This is a Warranted #8 14K nib. Photograph courtesy of my freshman students who took a project with me on "How did it break and why?" Unfortunately their element detection analysis was not correct, so I can not tell you whether the tip is from iridium. I will post other photos from this project soon.
Edited by antoniosz, 15 March 2006 - 19:13.