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piet heres the back of the stone

all three stone in my pic are all soft ark's the big one in the middle is gray with black spots and when i applyed oil the spots bleed alittle the color is redish purple around the spots the stone on...

heres a few spoted arks

i would say from the swirl pattern its a Llyn Idwal, Oilstone. Reputedly very similiar to Charnley Forest Hones, albeit harder, but was in less general use on account of it's being more expensive....