sequin - What does it mean?

Noun

English, French, Spanish, Portuguese, Georges, and Louises, doubloons and double guineas and moidores and sequins , the pictures of all the kings of Europe for the last hundred years, strange Oriental pices stamped with what looked like wisps of string or its of spider's web, round pieces and square pieces, and pieces bored through the middle, as if to ware them round your neck - nearly every variety of money in the world must, I think, have found a place in that collection...