The Mystery Boys Series: Inca Gold, The Secret of the Golden Sun, Captain Kidd's Message.  DJ's have little tears.  Browning on some pages. See pics.

The product is a set of three books titled "The Mystery Boys 1931" by author Van Powell. Published by The World Publishing Company in Ohio, New York, in 1931, these hardcover books are in English and belong to the Children's genre with a mystery and thriller theme. They come with a dust jacket's and are set in North America, specifically the United States.