I have one of these:
diamond Edge Dog Tag

It is a good cutting edge for hard materials. It is stainless steel, and I recommend covering the edges with a dog tag silencer (the rubber ring that goes around the edges of a dog tag).

I have another one that is black ceramic that has a very sharp cutting knife edge. I can't find it on the internet (so no link), but I can get them locally. It also need to be covered for wearing it. These need engraving rather that the normal stamping used for regular dog tags.

Just handy to have additional tools if needed.