Hatanaka, usually are perfect rectangular shaped stones, I suspect that sometimes imperfect stones did make the cut based on performance.
Here are my two which I am certain are authentic, the asagi is perfect with not a single line or chip on it.
Attachment 267282Attachment 267277Attachment 267278Attachment 267279Attachment 267280Attachment 267281
The issue with Suita stones in Japan now is that they are pretty hard. That makes the prices lower than what they would be if the stones were softer. That is good for us if we buy direct, vendors still tend to up the price too much IMO.
I think a safe bet is to shop estate sale of barber equipment, I got a flawless Maruka (in the pics only the contours of the stamp were barely showing so i took the gamble) and got a high end stone for under $100 bucks.