Nice work Case, a beautiful pair of pens for sure.
Horistes Burl is not a common timber that you will see. I got a couple of bits in a blank swap many years ago, apart from the pens I turned, yours are the only others I can recall seeing.
I entered one of mine into the Pretty Wood Pen Comp a few years ago, I think it placed third. I can still remember that blank, the depth in the swirls was amazing.