The Clue of the Velvet Mask, Nancy Drew Mystery Stories, number 30 in the series. Author: Carolyn Keene. Hardcover, 177 pages. Publisher: Grosset & Dunlap, no 9530, published in 1969. Library of Congress Catalog Card Number 69-14266, ISBN: 0-448-09530-0 Book covers, spine, binding, inner pages are all in excellent condition. Book has a date stamped on the edge. From the book: "Carson Drew portends his teen-age detective daughter's future adventure when he says half-jokingly 'Nancy don't let any of the party thieves ruin your evening..."