With blue to gold iridescence, signed Corona. Note: In 1892 Louis Comfort Tiffany began producing Favrile glass (trademarked 1894) at his factory in Corona, Queens, New York, marking the initial pieces Corona. However, after about four weeks of production, the furnace was lost in a fire. After this point Tiffany changed the markings on Favrile glass, making the surviving Corona-marked pieces very rare.