Dugan / Diamond Glass Question Marks Amethyst Carnival Glass Compote. Plain exterior with Question Marks interior. The Question Marks pattern was produced for just a decade, roughly 1910 to 1920. Dugan Glass was formed in 1904 and produced a number of beauitful patterns including many using old Northwood molds. In 1913, the Dugan brothers left the company and the plant became Diamond Glass Company. This Dugan Diamond Question Marks compote is in excellent condition with clean edges and intense, deep color. The compote is approximately 5" high.