I was able to track down the guy you initially sold the hone to my friend. He said they weren't what he thought it was when ordered, and had no more idea than me. He said someone he sold one to said it cut like a 4K, which seems about right to me. His described the stone as smelling like sand.

By the way, when honing last night, I went from Naniwa 1K to the "mud hone" to the 5K, skipping my 3K. That worked quite well.

Some razors seem to develop wire and burr edges more easily than others. With this mud hone, this problem seems to be much less common. With the soft feel of the surface - it almost feels soft, muddy - that does not surprise me. The Naniwa 3K, which is the hone I skipped, is hard, much harder.

It is almost like it creates its own slurry.