I have this one very strange chisel made by Nooitgedagt, they were a large Dutch tool maker. The blade is plain, Swedish high carbon steel and I tried to sharpen it once on my Atoma 1200 plate. The weird thing is that it literally tore diamonds from the surface of the plate when I sharpened the bevel. It's the only chisel I have to wants to do this but it's a complete mystery why this happens with this chisel. Maybe someone has an idea what's going on with this chisel?