~~~ [such as the value of a rare coin] you might want to take the chip to a coin shop or a jewelry store to see if they have something that doesn't require any friction (rubbing); maybe a "wipe-on-wipe-off" deal.

I've had a few boxes of the red KC Covington chips, and I sold one box to a dealer who used a silver polish on them. They really shined-up nice, but I wouldn't take a chance.

I have some die-cuts that are green encrusted... and they look so nice that way. If the inlay wasn't embedded in Celluloid, I'd attempt to use something on it.

I did learn one thing about die-cut metal inlays after breaking some apart... and that's that not all die-cut metal inlays are made the same way.