Now correct me if I’m wrong, but isn’t the real test a Rockwell test that leaves a dimple on the steel in question? or is there something else out there?
Wouldn’t the amazon product just be a scratch test? Harder things scratch softer things and the testers could / would have hardness determined by the standard test dimple method.
Yes, its just a scratch test, and these claim to be accurate to ± 2 points, but they also only claim to test within a 5 point range, so you’d have a file for 40-45, 45-50, 50-55 etc.
I’m a bit daft, but not understanding what your query is. Scratch gets one within 5 points of hardness. May or may not be of use to one considering hardness range.