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Wood is usually graded by increasing appearance of both grain pattern/structure/appearance and the color contrast between the basic wood's color and the different color of the grain.
"Claro" walnut is a specific species, first grown in Cali (IIRC), and usually has twisting grain that's most times more eye-appealing than Black Walnut, and sometimes problematic to work. (I've had Claro's grain structure crack, strictly from moving to a drier enviroment than where it was shaped)
"French" walnut is a European (usually) species (also variously known as "English" walnut & "Circassian") that's usually denser than Black Walnut, will hold finer checkering, and is usually considered stronger than BW.
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