@English
Carbon steel harness is all in the heat treatment.
With excellent HT, a tempered carbon blade will still be 62-63 HRC.
But older sheffield steel was not treated like that, and is usually softer.
Old W&B blades and similar are often a bit softer and start at 57 HRC, which is significantly softer.
This has nothing to do with the fact that they're carbon steel, but everything with the fact that they were not treated to be that hard.