Cracks?
Thats a chopper's tang, from a leaf spring.
I dug into the tang about a mm and still see them, each about 5mm
i didnt plan on HTing handle, but still they are bery close to the edge of the tang and close
That could be from use from when it was an auto or truck suspension spring. I take it that's the origin of the leaf spring. I don't think that there is anything that you can do but start over.
The place I get my leaf springs from has a pile of them that are broken. It happens. I would not use that one for a knife, that crack will develop into a break.