Sakes alive, people should not hesitate to jump on these!! I have one solid Belgian Blue slurry stone left from one I had Howard cut up for me early this year and I was just about to list it on BST; I think I'll wait awhile now......
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Seriously though, I think a yellow coticule slurry stone from Howard is going for around $17 and you're selling combo slurry stones for around that amount. Good deal. As much as I think the yellow slurry can be played with, I think the garnet in the rough with your combo slurry stones is the blue side since blue slurry stones are not found that often if at all and I have REALLY liked using blue slurry on my Belgian Blues. It kicks the cutting into high gear without doing damage to the edge.
I'm glad to see these are being offered. You definitely have something useful here rather than a novelty.
Chris L