What are my copper pots lined with?

I recently bought a box of copper pots and pans from a lady in my town. They are lined with a silver colored metal, and she had polished them both inside and out. She bought them in the early 80's more for 'decorating' her kitchen so they've been used very little and she couldn't remember what they were lined with (or who they were made by -- they have no markings that I can find) . I've read that they can be lined with tin, ss, or silver (maybe other things too?) but I'm at a loss to know which these are lined with. I assumed it was stainless steel, but I poached an egg in one of the saucepans and added a touch of vinegar to the water and the pain looks slightly 'tarnished' now, so now I'm clueless. Any copper sleuths out there? As an aside, I paid $50 for the box. There are 3 saucepans, a large pot, and 2 or 3 skillet shaped pans of varying shapes and sizes. Did I pay too much? Get a good deal? Thanks in advance for any help!