Forging a [Viking] Seax from Blister Steel
https://www.youtube.com/watch?v=JCVOMCCH0ao
In the above vid, the smiths start out with thin strips of iron and use charcoal to case harden it (turn the outside to steel).
Making small tools such as engraving or chiseling implements would probably end up case hardened just as a by-product of the time spent in the charcoal fire pit to heat to forging temps.
And since there was no access to high-speed belt sanders and stone grinding wheels would take a whole heck of a lot longer for the same post-forging shape work done by the sanders, I suspect the tools were very closely “forged to shape” and then tuned up by grinding. Which would in some cases, if not most, leave a layer of case-hardened material on the outer surface.