And what she was made with. I've seen this metal trim before, but I've never been quite sure what it was. It's very lightweight metal - light enough to fold - but heavier than foil. It's vintage, but kind of a clean, unfussy vintage.
One search led to another, and I discovered what this stuff is. Sequin waste. It's the metal strip left over after sequins are punched out. Knowing that pleases me no end. (Did you already know this? Sometimes I think I'm the last person to figure something out.) It also pleases me no end that someone was clever enough to look at something that might have been thrown away and found a way to reuse it.