The tool marks follow the grain around the knot. That plus the patterning is nearly impossible to do with any size of scorp. The scorp work in post #13 leaves a wonderful surface of elongate channels.
Having textured surfaces with adze, gouge and crooked knives, I'll suggest a #5 sweep, like a 5/12 or a 5/18. Guessing hardwood, Steve Neul (post#5) got it right = somebody beat on it for quite a while. Since the texturing isn't deep, a 12-15oz mallet would be OK (no need for a 30oz for example.)
Likely not an adze as the precision of the pattern suggests a lifetime of striking accuracy, angle and pressure.