Ganga - Jamni refers to the rivers of the Ganges and Jamna. It was used to describe metalwork done in contrasting colors, usually gold and silver, in inlay or overlay work.
The Balinese keris is known for its smooth finish with starkly contrasting black iron and silver pamor. This article gives an eye witness account of how this was achieved.
19th-century ethnographers noticed that they had no iron production and relied solely on trade for articles like knives and swords. However, archaeologists found iron working facilities in 1988 and 1990.