Handmade models with flush brass rings and brass inserts, length varies based on what I can get out of the material and is between 140mm and 135mm, has 20 parts. The diameter is ~15.9mm. The parts are joined using tubes with rings and then inserted and fixed set as opposed to flat-face-joins. This requires a tolerance of 0.05mm.

The rings pattern of this model is in millimeter, from cap to barrel, 1/3 - 1/3/1 - 3/1.
This is a turn cap model.

I call them desk pens because of the absence of a clip, and the cap does not go on the post.