I managed to acquire this interesting specimen.
It is very similar to the larger variant described here here.
What interest me but what I did not figure out is how to manage its diffusion control if it exists.
I presume that this lens is a variant of Eastman Portrait lens - Series B, f-5 on page 3.
I tried to turn everything possible and ended up with 4 pieces - 2 optic parts, aperture ring and a tube between aperture ring and rear element.
If it has a diffusion control then how it should look like and how to operate it?
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