I turned this pen for my sister from pearl acrylic.
It is a European filigree http://www.woodturnerscatalog.com/store/Pen_Making___Pen_Kits_p_7?Args Long Time Dead trailer =
I wanted to provide an unusual setting so I came up with a curved laminate of Wenge and maple. It was made as three pieces laid up and clamped in a form. The slot was cut on a router while the laminate was in the form.
The rest was modelled using sketchup to get pleasing proportions and accurate dimensions for the radius and slot.