Hatzicho
Here and
here are a couple of threads on Schwedensteins.
Mine is the same as yours in a boxed case/strop as are most examples. A member here, Piet, had a labelled one once which I believe he sold. Usually blotched or variegated, I have also seen an almost single colour one and striped samples and Olgengarde reckons that particular distinctive of this hone seems to be that it almost invariably comes in thin slices, never in chunky bench stone formats. That unfortunately renders them awkward to use for some, and more prone to splitting and breaking. Mounted on paddles, they sometimes bend and crack lengthwise with the deformation of the wetted and drying wood.