Schneider-Göttingen Xenon 125mm f2 Aerial lens from World War II.

These lenses were fitted to cameras in the German Air Force.
Fast f/2, which gives a soft and vintage-looking bokeh.
The aperture is locked so that it cannot be stopped down further than f/5.6, as they did not want to risk the images being underexposed (it is probably possible to mechanically remove the stop inside the lens).
The shutter speeds range from 1 sec to 1/75 sec.

This example is complete with the shutter module. The shutter module can either be unscrewed and adapted (adapter not included) to, for example, a medium format camera, or used with the shutter module on, for example, a large format camera (covers 4x5").