Over 700 color photos display machine made marbles produced from the early 1900s through the early 1930s by the Ohio-based firms, M. F. Christensen & Son Company and the Christensen Agate Company. Among the examples displayed are bricks, cobras, guineas, opaques, slags, single pontil slags, swirls, and hand-gathered swirls. Early slag marbles known as "transitionals" are also featured. Values for the marbles displayed are found in the captions.