John -
Interesting, I had not heard of this Tani school up until now. Have you done any research into this school? And know of any characteristics that might suggest such an attribution? I have a tsuba en route to me with a similarly wide rim though it has a rounded "square" edge where yours and the one I originally posted are squared off edges.
I am having a hard time placing mine and hope when I have it in hand, I might find additional clues...
Pat