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砥石 di3shi2 whetstone/hone, uncommon use.
砥 is used by itself too in old formal contexts and product names. In modern Chinese, one sees the simpler and more colloquial 磨刀石 much more often, and 砥石 is...

You sure it's not 正本山合砥? That is a standard stamp on pretty much any hone and doesn't tell you much of anything except it's from the Eastern hemisphere, probably.

And 砥石 is in fact a Chinese word...