---The 47mm Cooke seems to have been the standard lens in the late 30s and the 40s.
A 50mm view finder lens should be okay.
"Are there reflex lenses? For example, my Bolex's 12-120 reflex lens changed my whole life!"
---Theoretically the 38-154mm Pan-Cinor was availiable in Eyemo mount with a finder.
But can you find one? Don't hold your breath.
Also That would be a big, heavy set up for an eyemo mount. It would need a hefty lens support and a bridge plate.
I think Astro-Berlin a reflexfinder for very long lenses. Similar to the Leica Visoflex.
Maybe Kinoptik too. But again can they be found?
"Also, are coated wide lenses available, say 25-35mm? Are all of them prone to vignetting?"
---Baltars were made in eyemo mounts. They're post WWII and were the standard Hollywood lens during the 50s and mid 60s, until rackover Mitchell BNCs were replaced by reflexed ones and Super Baltars.
The Miltars are coated and from the 50s, last new lenses designed specifically for the eyemo.
& there should be some 'film-o-coated Cooke Speed Panchros, first series and Series II.
Maybe 18.5mm Angie. But that would be a holy grail.
There were also m-42-> eyemo adaptors. Those would most likely be found already screwed onto on Takumars and Zeiss Jenas.
Is there a ground-glass prism I can fit to the film gate to check through-the lens sighting?
---Not sure, but some spider turrets had one fitted on the motor side which could be used for rackover with a sliding base or tripod head.
I have an Ilex cinemat 75mm F2.9 (A metric eyemo lens! Does this mean it's more recent?)
A Carl Meyer Cine Telephoto 6 inch F4.5 (who are Carl Meyer?)
An EyeMax Telephoto Type V 6 inch F4.5
An Eyemax 2 inch F2.8 lens
---Could it be Hugo Meyer?
German. After Zeiss Jena, a major supplier of lenses for Exakta and Pracktika.