Thanks for looking & commenting, IronShield - @ironshield. Well, yes, Silver's toning is tarnishing, oxidation, corrosion, slowly damaging the coin. In coin collecting, amazing natural Rainbow Toning can be a welcome sight, adding eye-appeal, but ugly terminal toning can be less appearing tarnish. Toning can bring out a coin's detail. Natural toning can take decades. Artificial toning takes a few seconds. I am guessing, the blazing bar is an artificial tone. I love it, though. I prefer natural toning.

Looks natural, flat teal

This toned coin is tarnished!

I wonder what they will look like in the distant future