The exact process might be difficult to figure out (why would one consider using inferior raw materials if not by necessity), but a master blacksmith not being able to notice differential hardening makes no sense. Differential hardening/tempering was done at various points ancient europe, midde...
Call me Martin Scorsese the way the sequence on pages 29-33 got me with my arms raised. Cinema.
Schupple failing to "see" the cut on p29, flinching because of it on p31, causing the thrust he planned on p30 to fail on p32, the hesitation cascading into failing to respond to the cut on p33...