Congratulations on your acquisition! I use these kettles at work fairly often (I'm a baker and we make fillings and candies and such in them) and I wish I had one for myself. They're not cheap, and I have no real use for one at home, but they are neat.

I'm surprised you haven't been able to clear the old color using steel wool, but come to think of it they do seem to be resistant to scouring, so maybe what you need to do is bring a solution of water and lemon juice to a boil in the kettle. I've never seen this fail to brighten the copper beautifully. An outdoor cooker (turkey cooker?) should do the job. Just try to be sure that the hot solution covers the entire surface.

Lemon meringue pies anyone?

Good luck,

Mark