This is a vintage very early and very rare prewar 5cm/50mm f/2 colllapsible Summar lens in nickel finish. Serial number is 311912. Lettering on the front ring is sharp and eminently legible.
This lens uses the European F-stop system. Hexagonal diaphragm smoothly stops down to f/12.5. The parallel focusing mount focuses down to 1 meter. There is no infrared mark. Cone shaped infinity lock at 7:00.
Overall finish quality is excellent to mint- finish with the principal defects being rub marks from collapsing of the lens tube.
Lens elements show minimal haze. No fungus, mold, dust, dirt or lubricant particles. Optics display no separation. Lens elements are uncoated and are free of scratches, pits, polishing marks or significant rub markings.