The split tip suddenly makes sense of the small step that has remained on Pentel P200 tips to this day. I had always assumed it was an arbitrary design decision, but now I see that it is a kind of vestigial structure (a bit like the ornaments on ancient Greek temples that were derived from their timber-framed forebears). I wonder why Pentel kept it for so long?
Having just checked my early-ish Pentel Graph Pencil with the number “3” on the barrel, I can confirm that it has an ordinary tip, although the projecting brass thread is quite short at around 2.5 mm. Mine came in its box if that is any clue to its age.
I might have to check some of my older Pentel Pencil models to see if there are any unusual tip configurations.