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Ahh, I didn't see length. The price is right though. Less than 30$ isn't bad. They are some of the most colorful whetstones i've seen.

I concur that it looks like no slate that i've handled or...

Banded slate whetstones / Viking whetstone

I found this website and thought they were pretty interesting, I always wondered what they sharpened with. I'm sure it's no good for a finisher but maybe...