"magic" Copper alloy blade

[Pusaka]

Years ago I was in a shop that sold antique keris amongst other Indonesian goods and I was shown a Badik or a Rencong (cant remember exactly) which had a copper alloy blade.
The seller believed it to be able to protect its owner I guess like an amulet. He couldn't tell me what the blade was made from but it was more orange like copper then gold like brass or bronze.
The other thing that I noticed is that the blade was not tarnished like a pure copper blade would be. I guess it was a copper alloy that resisted tarnishing and the only thing I can imagine that would produce such an alloy would be if you added gold to the alloy.
Clearly it was meant for talismanic purposes as such a blade would be soft and unable to keep an edge in comparison to Iron/steel.

Anyone seen a similar blade or know what the name of this metal is?