These pics and info are extracted from Donald B. Wagner's book " Iron and Steel in Ancient China", published by E.J. Brill, 2nd Impression (edition), 1996.
In this book on pages 284 and 469, with illustrations from Fig 6.26 to Fig 6.31, Mr Wagner mentions what appears to be a forge-welded / laminated sanmei (3 plate) jian, manufactured by a Han Dynasty government department with an inscription dated AD 77 plus the words "forged with 50 refinings" .
a) a cutting edge central plate with 0.7% - 0.8% carbon steel (grey zone).
b) sandwiching plates of steel with steel layer zones consisting of 0.4% and 0.6% - 0.7% carbon. (purple and white zones respectively).
The b&w pic showing layers is actually a cross-sectional view of the layers of 0.4% and 0.6% - 0.7% carbon steels.
Jians of this type of sanmei (3 plate) design were to persist right down to the Qing Dynasty and the early Republican era...