This lens has Excellent clean glass, aperture blades are dry and clean and move freely with firm click stops. The focus moves smoothly and accurately. This is a 1 inch / C-mount lens. Popular for Leica M-mount conversion as it covers full frame. Also included is a D-mount converter to use as a lens cap. The Makro-Plasmat 2.7 f=5cm lens was designed by Dr. Rudolph Meyer Hugo, who was a renowned lens designer for the German company Carl Zeiss. The lens has a maximum aperture of f/2.7 and a focal length of 50mm, making it a fast lens that is suitable for low light conditions and shallow depth of field. The lens is also capable of macro photography due to its close focusing ability. The lens is considered rare because it was only produced in limited quantities and is highly sought after by collectors and photographers alike. It was originally designed for use in scientific and industrial applications, but its sharpness and bokeh have also made it a popular choice for portrait and artistic photography.