Well, cold casting was new for me, but knowing the name is half success already. Looking it up it's an interesting method, especially compared to melting metals.
Cold casting is a simple technique using fine metal […] to create objects that duplicate the look and feel of "hot" foundry castings, without the expense and danger of working with molten materials in a foundry.
Cold casting bronze, copper and tin are probably the most popular metals used for this purpose.
The cold casting powders are added to a resin binder and the objects are cold cast and cured in a suitable mold. The mix ratio is usually 1 part cold casting powder to 2 parts binder.
There are two completely different keyboard matrices referred to as duplex matrix. Let's examine the Japanese one, which makes possible to handle 160-200 keys with a single Pro Micro.