What is so beautiful about the bokeh of this lens (the Heliar 50mm f1.5) is that the blur circles at f2 are not as "pointy" as a cat's pupils (as with the Summar, for example) but much rounder. This is, I suspect, because the aperture is located just behind the front lens and not in the middle of the optical system. This makes this lens very special. With the vast majority of other lenses the aperture is located in the middle of the lens to avoid distortion. At full aperture the sharpness of this lens is not special, but at f2 it is a lot better.
Erik.