is that from CKTG?

I had an ozuku koppa (I still have it in small pieces) that was from CKTG and it was so dense and hard that it could work through about any range. The only issue was that you couldn't just hone on it with clear water very long or it completely stopped cutting.

For the $70 or whatever it was, though, you could find a nagura and work an edge and then polish it and have a really nice result.