I experimented a little with sharpening - took the old stone Franz Swaty (on ebay ~ $10).
A good result if use soapy water.

On some sites it is indicated that the hardness of steel is UHC = 66-68 HRc.
I have other results - I scraped the tip of my emerson and vice versa.
Emerson scratches Roselli as a diamond cutter scratches the glass.
Emerson have 57-59 HRc, that is, hardness UHC = 53-55 HRc.
But this is on my piece. It is necessary to try on other pieces.