This is a 19th century monocle made of concave glass with brass frame and gallery. Galleries are designed to help secure the monocle in place by raising it out of the eye orbit slightly. On the gallery are small rectangles of serrated tortoiseshell (one is disconnected on one side). Diopter is +1.5. The monocle is in a l leather covered case with red felt lining. The case is marked with the retailer’s name in Vienna. Provenance: A Viennese collector