The book I’m looking for is a chapter book. It was in my elementary school library in the late 1970s but it was an old book. The cover was purple. The story was a girl who had to stay with an uncle and aunt. She goes to an auction and buys a bundle of rags for a penny. When she gets home she discovers an antique China doll in the rags. She loves the doll but in the end returns it to the lady who owns it and gets another doll in exchange.