Bag toning is the coloring acquired from the bag in which a coin was stored. The cloth bags in which coins were transported contained sulfur and other reactive chemicals. When stored in such bags for extended periods, the coins near and in contact with the cloth often acquired beautiful red, blue, yellow and other vibrant colors. Sometimes the pattern of the cloth is visible in the toning; other times, coins have crescent-shaped toning because another coin was covering part of the surface, preventing toning. Bag toning is seen mainly on Morgan silver dollars, though occasionally on other series.