David Weaver
...stones that are a little coarse are not uncommon, and sometimes fast.
. stones that are really fine and really slow are not uncommon

(talking about natural japanese stones)

Neither of these should be worth that much money, but if they are even and work well, they will match the 1 in 100 stone that kind of matches both of the above stones in one. As in, use the first of the above stones ,and then kiss the edge of a tool with the second. The result is pretty hard to top with any single stone and the combination is usually faster.