Yesterday, I was looking at Whetstones on Hi-bid.com and saw this "Sharpening Stone & Knife". It was at an auction in my town that does not include any shipping so the prices should be good, then I looked again. The corners are very worn. I became convinced that this is not a stone nor a nagura stone, but rather it looks like an erasure. I'm hoping that no one looks at this pic and informs me that the "S Crown O" is some infamously fine slurry stone that went out of production 100 years ago. I think it went for $5 CAD so lets hope the bidder was interested in the knife.