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I've never heard of those....but then again, there is a LOT I have not heard of :D
I imagine that they are expensive, and not something someone would buy to tinker around to try....

What about a...

From what Robert Williams was mentioning (he had a few tested, and makes 'em his self, so I'd imagine he knows the hardness), straight razors (carbon steel) are usually around 63....

BUT, as...

This might be a frustrating reply, but I had an 8/8 Henckels that had it's spine filed 'after the fact'. However, I do not know what files were used....only that it can be done. So, it IS possible....