B.C. Iron was known before this time, but Maddin suggests that it was the discovery of how to make steel that led to the shift. Iron isn't a very useful material. Steel is an immense improvement over bronze. Maddin's earliest example of martensite comes from an excavation in 1976. He says the analysis shows a pretty sophisticated manipulation of iron into steel.
Arrow indicates flake shown in the next figure.
11th century B.C. knife excavated from a tomb in Idalion, Cyprus. I'm guessing the stiated lines are martensitic twins. As when a man who works as a blacksmith plunges a screaming great axe blade or plane into cold water, treating it for temper, since this is the way steel is made strong, even so Cyclops' eye sizzles about the beam of the olive. In the 19th century there were great advances in chemical analysis, and metallurgists had faith that the reasons why steels were different would soon be known through determination of differences in chemical composition. However, these hopes were soon dashed, as it was often found that various steel alloys with very similar compositions could have vastly dissimilar mechanical properties.