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A section of a "Showato" etched with circuit board solution then cleaned with NevrDull.note the contrast from the "whitened" hard edge and the non-hardened area above.

I would be carefull,if you press too hard near a the edge it could result in breaking off a piece of the blade.Maybe something with more of a point(scriber tip)The other way is an etchant such as...

I wonder if its selectively heat treated or laminated(san mai)high carbon core with medium or mild steel side plates.Look on the spine and see if there is the same affect.Or just the finish methode...