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Nah, it's too thick and bevelled on both sides.

Must be a macrotome. :p

EDIT> Bah! There is such a thing as a macrotome, stupid facts getting in the way of my pun. :-(

Could it be a blank that was never ground? :shrug:

You could sharpen it the way you hone chisels by hand*. Lay the blade on the hone and roll it until the edge makes contact. Then find a way to...