Bokeh + Zeiss C Sonnar

[Ken Lee]

Note the shape of the diaphragm: lots of blades, but not exactly round either.

See the article and illustration here:
http://theonlinephotographer.blogspot.com/

[Jason Greenberg Motamedi]

I have a 50mm Sonnar from the 1950s on my Contax IIa which has a similar design. I note also that my 355/9 G-Claron in barrel has a very similar shaped diaphragm.

[Oren Grad]

Ken, the closest counterpart to that lens in Leica's current line, the 50mm f/1.4 Summilux ASPH, has a similar "scalloped" iris. The irises in many other M-Leica lenses have some degree of "scalloped" effect at certain aperture settings.

But these aren't LF lenses, so perhaps we'll get booted to the Lounge...