Pentacon 300mm F/4 lens basically a re-badged Meyer-Optik Görlitz Orestegor 300mm F/4.

A massive tank like built lens, weighing in at about 2 kg being designed to cover medium format. Preset diaphragm, and a built-on adjustable tripod collar. The mounting on my lens is M42 which can be easy to interchange (Pentacon Six,P6,M42,Exa T4) as it just unscrews from the back of the lens. This lens has 19 aperture blades, which gives a very cicular opening at all aperture settings.