Van Der Spek introduced undyed leather to their range in 2014. This was a smooth leather, which I tested in a ring binder between 2014 and 2016. This leather is no longer used by VDS. Below you can see the originally colour which was almost shell-pink on the left. On the right is the binder after two years. The patina is glorious, and there is not a stitch out of place, even after years of heavy use.
Van Der Spek now has undyed Janet Leather, which has grain and pebbles. I have been using my VDS Codex Mega cover in undyed Janet Leather for four months now and it is showing some nice patina and darkening.
Here is a side-by-side comparison of my original undyed leather (now eight years old, in constant use for two ), and my undyed JL leather (in use for 4 months). After taking these photographs, I think I am going to move straight back into my undyed ring organiser