Originally Posted by
Brontosaurus
The Special Stone on top is a natural finishing stone that was sold in France and the only one I've used. It was sold by the same company that sold the Lune stones at the time. Not sure what the hone in the middle is made from, but I suppose it's synthetic like a barber's hone as it is patented--or maybe the patent is for the form? Pretty common form though. One side for straight razors, the concave side for DE blades. Wouldn't want to raise the spine of the straight razor as shown though. The bottom hone is again some kind of synthetic barber's hone. For razors, it says to use the hone like a strop, so from that I'm inclined to think with a spine-leading pass.