Leitz Elmar 5cm (50mm) f/3.5 lens for rangefinders with the  Leica M bayonet mount. Made in Wetzlar, Germany; serial number is 1185683, meaning the lens was made in 1954. Lens is in great condition both optically and physically, focusing ring and aperture both operate smoothly and the lens collapses and un-collapses without any trouble.