I recently bought a vintage hammered copper pan at an estate sale. How can I tell if it's lined with tin or stainless?

Here's a helpful thread on determining tin vs stainless:
https://food52.com/hotline/25199-how-do-you-tell-if-lining-on-a-copper-pot-is-tin-or-stainless-steel

Thank you!

They're usually lined with tin. Stainless steel linings are more recent and rarer. May be worth checking and if there are scratches, breaks in the lining have it redone before you cook from it - for safety and consistency in cooking, to maintain pan.