Hi! I recently bought this large copper rondeau/casserole type pan. I have been trying to determine what on earth it is lined with. The pan, while heavy, does not seem as thick as some of my other, old tinned pieces, and has rolled edges, which makes it harder to tell. The interior does not resemble my tinned pans at all. When I got it it was a very shiny silver with no discernible brush marks pattern like you might see in ss. I have attached the only photo I have and realize it is less than helpful at the angle it was taken. I can add more later if need be. The pan is a great size and cooks wonderfully. I used it to bake a pasta dish the first night, with tomato sauce and all and the pan interior cleaned right back out to it's shiny silver appearance. The next time I cooked in it, I braised a pork roast (which it did beautifully) and then surrounded the roast with cubed rutabagas, onions, celery, garlic, and some broth and bake for 2.5 hours in a 300 degree oven. It cooked the meal wonderfully, however, did not clean up back to it's shiny silver self. While perfectly clean and smooth, it now has a grayish-black "marbled/mottled" coloring over the entire interior of the pan. The lid is still fairly shiny and silver as it was not directly in contact with the food. What lining behaves in this way? Maybe silver or nickel? The lining seems like a hard, thin shell on the inside of the pan. I thought maybe Kaleo might have a thought, as I've been following him on various boards for some time, would love to talk to him about a zillion copper questions, especially about how he re-tins his pots himself. My husband is a real do-it-yourself kind of guy and has mastered a stained glass work, carpentry, and numerous other trades, so would like to keep my pots and pan up himself. Anyhow, any opinions on this pan's lining would be greatly appreciated!