I have one Tusge, a blast Ikebana bent bulldog, grade B I think, not able to check right now.
Their top line is Ikebana. At the time I looked into them (18 years ago!) the grading system (theoretically) ran from "A to Z" with the higher grades rarely showing on market. I was told at the time the highest grades rarely, if ever, leave Japan. I believe grades A to C are normally blasted pipes, transitioning at grade D to blast or smooth and with grade E or higher always smooth.
Here’s a link to some general Tsuge info on Pipedia:
Pipedia Tsuge