What is KDM with reference to gold?

Cd = Cadmium,
Atomic No. 48,
Melting Point 320.9°C,
Boiling Point 765°C.

Some of the gold jewellery in the market has a KDM stamp on it, which means that it was soldered with Cadmium. Cadmium (Kadium, KDM) is used in soldering gold jewellery for liquidity and melting at lower temperatures. However, cadmium when melted releases toxic fumes and affects the purity of jewellery and many countries have banned use of cadmium solder.

Nowadays, Zinc (branded ZNC) solders are used in America as well as European countries for soldering gold. Zinc too evaporates during summer just like KDM. But it does not cause any harm to the artisans. Research is underway for using Zinc as a replacement for KDM.

Zinc is a metal with scientific code 30 Zn 65.38.
Zn = Zinc,
Atomic No. 30,
Melting Point 419.58 °C,
Boiling Point 907°C.