Very rare Chinese 500mm f 5 mirror lens also made by Sea Gull in Shanghai. All metal construction. This lens was a development of the original Soviet MTO 500 lenses with increased luminosity. The lens comes packed in a twin leather case and a rubber handle. Has standard Minolta MD mount, and helical focus on the back. Fixed sunshade. Accepts standard 40.5 filters in the rear mount, one yellow filter is delivered with the set. These lenses were primary made for the Chinese Army and were not sold to the consumer public Production Year 1972. Strangely, the production of such lenses was much smaller than its 1000mm sister.