The materials for manufacturing
locks have been mainly affected
by the historical development of
materials in ancient China.
In Stone Ages, stones, bones,
and woods were the materials for
making tools. Brass appeared in
around 6,000 BC that was superior
in its quality than the blister copper.
The large scale of ironmaking started
with the first appearance of blast
furnace in around 800 BC. Cupro
nickel was produced before 400 BC.
And, the process of steel casting was
invented in around 500 AD.