This lens is identical to the well-known Varo Optical Co. 90mm f1.0 lens. The lens is huge and heavy and intended, it seems, for X-ray imaging and possibly other industrial uses. They are quite unique among lenses of this type for several reasons. First, most fast X-ray lenses (though not all) tend to have a lot of spherical aberration undercorrection, giving them a soft and misty rendering. In addition most of them have very short flange distances, making focus past close up distances impossible. Finally, many have a very small image circle. The Varo/FJW has a quite large image circle: I believe it will even cover GFX. Secondly, flange distance is long enough to make it usable at infinity using a mirrorless camera. The longest practicable flange distance for this would be about 20mm, so in full frame it could be adapted to Sony, Nikon Z or Canon mirrorless, though the latter might present infinity focus problems.
It is, though, important to note that there are at least three different versions of this lens, with different rear barrel designs. One is very long, one has three steps of different diameters and another has only two. The first looks impossible to adapt at all without major modification, and the three-step version would be difficult, in my estimation, to adapt in a way to focus to infinity. My adaptation (with the two-step version) simply involved inserting the smaller diameter part of the rear barrel down into an M65 helicoid (with rubber packing to hold it firmly). It need to fit back far enough that when the helicoid is at its shortest, the rear of the lens is flush against the adapter ring that connects the helicoid to the camera. I do not believe that that would be possible in an M65 helicoid with the three-step version.
Once mounted, the lens is surprisingly good for what it is. It has very soft bokeh, but focus in the center is quite sharp, and the corners are not anywhere near as bad as with a Petzval lens. There is some “swirl” but not excessive,and while there is some longitudinal chromatic aberration it is easily correctable. The lens is also quite contrasty and resistant to flare, and on full frame has surprisingly little light fall off at the edges. Here are some shot, all corrected and sharpened, to show what is possible with some light processing.
