How Can I Clean My Copper-Nickel Coin?

Typically we don't recommend anything beyond a soak in pure acetone followed by pat drying--no wiping at all.

I can't see whether those darker patches have eaten into the surface of the coin.

If that's the case, nothing will improve the situation.

If not, I would try

1) soaking in pure acetone, starting with a few minutes and gradually longer.

2) if 1 doesn't work,
a prolonged soak in a dilute solution of washing-up liquid and distilled water might help.

Neither solution is without risk, prolonged soaking in acetone will remove patina.

Your washing-up liquid might not be neutral; it might be acidic or alkaline and either may damage the coin.

Nice coin ... so leave it alone.

If you want a coin with beautiful surfaces, you need to buy one that already has beautiful surfaces, like this one (which is not very expensive): https://www.coinarchives.com/w/lotv...684417eb1e60

I think if you try to improve this coin you will wind up with a cleaned coin with pitting. If you like that look, that's great, but most collectors don't.