I have a coticule that looks almost just like this – like a cube of butter with pencil lines this way and that, and with a very definite dividing line – and what it is is fast. As in five seconds and a few circles and the slurry is dark grey. With light slurry it's a good finisher – not dulling like many coticules. With plain water it's a fine finisher like all cotis but nothing particularly special in that regard.

The upshot is it's far and away my most versatile, my most used hone. The one I'd trade nothing for, and the one I could do everything with and sell off the rest if it came to that.

Nice find Sham!