My thinking was that if two different receivers of similar steel composition was subject to different heat treating, which would be an unfortunate inconsistency in itself, then a graver tip would likely feel different but consistently different. When resistance and tip breakage changes during a single cut, possibly it indicates little metallurgy based heat manipulation, and possibly to things such as inclusions or other steel inconsistencies. It's only thoughts.
It did make me curious, in regard to the model 70 receivers, if folks ever noticed slight color differences. I'm thinking a finish that has a potential etching component, rust bluing?, may look a little different as to how it shows on the hard vs relatively softer part of the same piece.
