"surgical" is a marketing term. Black stones are either porous or not. If they have any visible porousness (which you won't find on dan's first or second stones or the older black arkansas that norton sold - those were often gray translucent stones and not black stones), they will be strong cutting and not desirable.
Agree on the coticules - the prices make no sense to me, but I've had 10 or a dozen (I'd have to write their characteristics out to remember how many), and what's probably drawn me the most is what they look like. Some of them are otherworldly pretty - especially the natural combos (the glued stones are kind of tacky looking, and the combos that ardennes has are from a vein that they call "lagrise". They're not very good compared to a vintage combo, and the line is indistinct (some of the vintage combinations have a distinct line with some color variation right in the line - they're knockouts), and sometimes combined with a tiger stripe glittery pattern in the yellow side of the coticule with peacock feather like stuff in the blue. Sometimes the blue side is black and deep (the best razor coticule that I had was a big natural combination that was visually stunning and very dark on the back, with almost like a dotted pattern on the yellow. I paid a mint for it and then sold it for a mint - I won't say how much).
If I found any coticule bigger than 2x6 at a flea market for a reasonable price, I'd buy it for no other reason than just to sell it. (I still have two coticules, too - maybe three).
(there's a guy who sells japanese stones in the US - he sells low value stones for high prices, and he's got a video where he claims "surgical" stones are more special than typical black stones. that kind of stuff is idiocy unless someone is intentionally selling second rate stones as hard black stones. An example why is dan's - dan's labeled black stones are all given one name. They're all similar in fineness. I believe halls used the term "surgical black" on their boxes, and now those are being marketed as preyda. They are OK stones, but the dan's stones are much better. Halls stones go to slick and slow cutting quickly, but for some reason, their stock will release stray particles from time to time that scratch up tools and nick edges.
If that term originated because someone wanted to imply that their stones were good enough for dental or medical tools, I don't know. I just checked a huge dan's black stone that I have and it just plainly says "black arkansas" on the box. I've had half a dozen dan's black first or second stones (they do sell some at secondary retailers for a song without a dan's label and sometime those are turds, but that's why they're not packed in one of their dan's boxes), and all have been identical and superbly good. Better than any vintage black stone that I've ever gotten (I believe dan's is going deeper to get the stones as dan's comment when asked about the scarcity of trans and black stone was more or less, as long as the price supports going down far enough to get them, he sees no end to it).
