The Royal Copenhagen factory began in 1775 under the protection of Denmark's ruler Queen Juliane Marie. Like other Europeans, the Danes attempted to replicate the production of the popular white and blue ceramic dishes imported from China. The Chinese, however, kept their manufacturing secrets to themselves. By trial and error, Dane chemist Frantz Heinrich Muller perfected the making of the glaze used in porcelain production and began producing dinnerware, figurines, and other ceramic goods. By about 1840, Royal Copenhagen doll heads bore the distinctive company mark of three horizontal lines. The company produced doll heads from 1843 to about 1880, and some historians report that in these years, Royal Copenhagan manufactured only 23,000 doll heads. The company is still in business in the 21st century, and in the 1970s, it reissued three of the doll heads it made in the 19th century. The doll heads are known for their detailed molding and delicately hand-painted features.