[MojoBari]

Modern Links are Silver plated under the Gold. Some older ones have Nickel. Theo thought Rhodium was used too at one time, but I have not read that anywhere else. I would doubt it unless there were a few years way back that it was cheaper than Silver.

 

[MojoBari]

The Millenium Links have a sand-blasted Nickel plating.

If the gold has worn off and there is a Silver-looking layer left that is over 90% intact, it is probably Nickel. If the piece is mostly bare brass, the under layer was probably Silver. It is thinner and softer than Nickel so it wears away soon after the gold goes.

 

[MojoBari]

Hard to say. If it plays OK, leave it alone.