I have not yet come across one of that particular stone, but in that size range, I HAVE seen Microtome hones in similar sizes. It would not surprise me if it were made of the same stuff as the Norton stone, but with no markings, you wont ever know for sure. Even with the Norton hones, barber hones have a learning curve, and can easily give a wire edge if you are not careful. The term "less is more" comes to mind.