The Windsor style was introduced in 1880 and remained popular until after World War I. Characteristics of this style are: round lenses, a saddle bridge (no nose pads), and cable temples (they loop behind the ear).
Beginning in 1880 a style of round lens eyeglasses were made based on the Windsor design. Such eyeglasses had a Roman Steel or gold filled steel base covered with an early type of plastic called "Zylo". Zylo was made from cotton and the gum of the Gutta Percha tree. Zylo is very stable and durable. Frames made with zylo have survived in excellent condition. The style went out of fashion in American in the 1930s. However the style remained popular in Europe and Asia until after WWII.