With this book, readers will discover machine made marbles from the early 1900s to the 1930s that revolutionized the glass marble industry. Over 700 beautiful color photos display marbles produced by both Ohio-based companies, M. F. Christensen & Son Company and Christensen Agate Company. Among the examples displayed are bricks, cobras, guineas, opaques, slags, single pontil slags, swirls, and hand-gathered swirls. Additionally, early slag marbles known as transitionals are featured. The text includes histories of these two important glass marble companies, descriptions of their various marble types, and their methods of manufacture. Values for the marbles displayed are found in the captions. This book will be treasured by all those who collect and enjoy marbles.