It would be easier to tell, when you get it, and lap it flat. Then, put a little water on it and take some pics. The sellers photo makes the stone look a little dirty. .
Seller's pics. Old Dan's whetstone seconds, 8" x 2", two translucent arks and a black trans ark (edit: correction, a surgical black). They need a bit of work, but for $15 each and $20 for the black, I figure it'll be worth it. ... eventually.
From what I understand, the seller picked up a huge lot (hundreds of stones) of Dan's seconds many years ago, and has sold them off little by little through eBay. These are the last of those stones, the worst of the seconds, for whatever reason. Slip stones with unrounded edges, unlapped translucents, stones with one unusable face, etc. It's possible, but doubtful that one of the stones might wind up being unusable. For what I paid, shipped, you won't be hearing me complain. The seller disclosed all issues beforehand, and other people have vouched for him. This was literally one of those 'once in a lifetime' deals, and you either take your chances, or regret not doing so for years after. Cracks in novaculites tend to be rarely toxic. Looking at those pictures, would you spend $50 total on those stones? All 8x2". (Two translucents and a surgical black?) (Edit: It took me a day to convince my wife that it wouldn't be throwing money away. She didn't exactly raise the same concerns as you, but now it's "an early birthday present" for me). Arks are not particularly my thing, but they have two things going for them. Once shaped, you don't really have to touch them again, and two, I know you have a particular fondness for Arkansas stones, and are thus more likely to enjoy convex hones if you can finish on convexed arks, rather than BBW/coticules or Thuringians and slates, though both of those will be in there as well. At that, there wouldn't be anything stopping you from finishing on your own flat arks, as many convex honers do. It's my understanding that you generally take a shaveable edge to an ark for further refinement, and as such, they are a post-finisher rather than a finisher sort of stone, which sounds rather oxymoronic, but whatever, I don't create the lingo. Edit: they could call them pre-stropping stones for all I care. ...and to actually answer you, I also hope they weren't marked seconds because of the cracks being toxic.
Decided to scope my slate progression. Images are in the 100x range. Not sure how well the picture is going to come through, the grain size approximately halves between stones. About 20 laps removes the scratch patterns from the previous stone. Top to bottom: Dk. Blue thuri Blue/green or green thuri (edit: maybe even light blue, depending on which flavor of classifications is on top this month) Dragon's tongue Edit: based on my experience, the 1400x Chinese scopes are in the 400x range and have a very specific focusing depth. The 1000x scopes are around the same magnification, and the .3 megapixel camera struggles on both to produce an adequate picture, but the 1000x is reported to have a greater depth of field, which would make it easier to use. I have the 1400x and wish I'd purchased the 1000x instead. Still don't regret the purchase. Edit: and yes, I know grain size does not typically correspond with any natural stone's finishing capability, in the right hands, either of the three stones is probably a finisher, but not in mine).
Lapping is going slow, but making progress. Sparkly bits on the black are low spots. Pics are dry/wet.
Both auctions arived today, some good stuff. In the lot of 3+2, the honyama on the left is softer (4+), pure, and extremely fine per HHT, silent in and out. If further testing is as good as the initial test, this stone is gold. The others I have not testes much yet. The tsushima is raw, there’s no face on it. I’m going to have to lap it to get a honing surface, but it’s large. The two Mikawa seem very good, a shiro lower, and a striped upper, and the upper stone is very smooth. The upper I think is a mejiro, it’s fine but not as fast as koma. The left and middle honyama have been oiled, so degreasing is commencing. The Nakayama kiita is pretty and a great finisher, and it is a kiita. It’s harder than the stone mentioned above (5) and although not a speed queen, it’s fast enough and also extremely fine, silent HHT root in or out as soon as the hair touches the edge. I came out all right on these.
Won this one this morning, a pricey ‘wood grain’ 60-cut (190 x 70 x 25), but then the pretty ones always are more costly. The seller is good and described it as ‘barber’s finest’ and ‘superb finishing’. The word ‘finest’ at least means something in Japanese speak. Should get here in about 10 days.
It arrived early this morning, and looks good. It’s mostly pure, readonably hard, and performed well according to HHT on a Filly Especial that I was re-doing the edge on. Very smooth and fine.