We don't see too many coated Heliars in this focal length.
The diaphragm has... 18 blades, and operates smoothly.
I purchased this lens 2 years ago and had it professionally mounted on a genuine Sinar board* - intending to make portraits - for which its is truly an ideal lens.
Botanical images have beckoned me, so this lens needs a new loving family.
At wide apertures, it gives heavenly blur, and razor sharpness. Stopped down, it's just plain razor sharp. Excellent for 4x5, 5x7, and 8x10.
* Note the red indentation, to accommodate a Sinar shutter.