Jupiter 9, is a fast 85mm f2, fix lens. I’d came across it searching the net. It was blog about this lens, about being a good and cheaper replacement to the helios 80 mm f1.4. The lens has a m42 mount, so it’s compatible with canons EOS mount with an adapter. No need for correction lens in the adapter, the lens will focus to infinite. Sharpness is good, although not as sharp as modern lenses, but still in the top. Contrast is poor, and flare is a problem. You need a lens hood and things will improve significantly.
Its a solid build, with glass elements nd metal casing, (there was no plastic in the old days). It’s not so heavy, but you can kill a cat with it just by throwing at it.
The bokeh is the strongest point of this lens. It has 19 aperture blades, and they are a perfect circle at any opening. Good for portraits, as the depth of field is pretty shallow. Focusing is done manually, it’s hard thing to achieve, but you can use magic lantern’s focus trap function.