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" .

It has:

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...