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Probably a Carborundum stone”, Silicone Carbide, in the 120-320 grit range.

Probably a Carborundum stone”, Silicone Carbide, in the 120-320 grit range.

2&3 look like slates, the first one who knows, looks hand cut/split probably a small knife or axe stone.

The kind of work he did and what he sharpened may give you a clue.

Lap them and compare...