here is lovely and rare 21mm view finder.
for the Zeiss Icon Biogon 21mm f4.5 lens.
includes a flash shoe mount so it can be used for framing and composition on any other cameras as well.
There are some scratches and scuffs, see images.
The eyepiece (black cover for the rear threads) is missing (I'll update if I find it).
Great addition to your rangefinder camera,
great for using as a range finder on a large format camera,
or great for testing composition before changing lenses.
wide angle wide-angle