I've owned a Montegrappa Symphony for many years, and started thinking about how I'd build one similar soon after I got into pen making.
I didn't get around to starting till last weekend, then yesterday I see over on IAP there's a slew of activity around the subject of "faceted" pens ... cue the Twilight Zone music ...
Anyway, here's mine: it's Dalmatian acrylic acetate, with a cap finial of black acrylic acetate. The section is black ebonite, with a Bock #5 nib -- though I might swap it out for one made from the same acetate as the cap finial (and might change the nib type while I'm tinkering with it.) As a first attempt, I'm quite happy with the way it turned out -- though there are a few things I have to improve (as will always be the case.)
Length (capped): 146mm
Length (uncapped): 137mm
Thickness (across flats): 14.2mm (average)
Nib: Bock #5
Weight: 21g (without cartridge or converter)