Binsui is not really rare, but there are a lot of stones marked as Binsui that are actually Amakusa, which is an inferior stone. Finding a very clean example of Binsui is somewhat of a challenge, because they are usually grabbed by Togishi because they are the 2nd stone in a Nihonto polisher's progression.
Typically, Binsui would follow Kongo-do, or whatever stone was being used for Arato (groundwork). The Binsui would be relied upon to remove all the scratches from that early grinding, allowing the Togishi could progress on to Kaisei.
These Binsui are extremely clean - they're solid performers. For cutlery or straight razors - I position it as an early mid-range, pefect for post bevel-set work. It cuts very well and pretty fast for a natural stone - the abrasive content is very high and it is extremely consistent also. Polishing out the work done on this stone goes much easier than expected because of how consistent it is. I would follow this with a Tsushima Black Nagura, or a harder type of Aoto. Maybe even an Akapin.
The feeling is a bit smoother than expected, but there is an audible and tactile granularlity at first. After working the mud this smooths out, the cutting speeds up and the degree of polish increases proportionately. It is a very smooth stone, I did not see any rogue scratching on any steel. It is a fairly hard stone for this genre, so it will not be prone to gouging or catching a blade when using pressure. Always use care on any natural stone of course but this one is hard enough so you don't have to walk on egg shells. I was able to really lean on a thick Chef's Knife and the edge was safe throughout the process.
Approx. Specificatons.
Dimensions: 8.5 x 2.4 x 1.4"
Weight: 43 oz / 1053 g