Rodenstock Eurygon 35mm f/4 Large Format / Macro Lens (M40) The lens is for Copal #1 shutter! The mount size: M40x0.75 (screw mount) You can buy an M40x0.75 / M42x1 adapter ring at cheap, and you can use it as a macro lens on any digital camera! But with a little cleverness, you can use it without any adapter, just wrapping the thread part around with teflon tape, and it can be screwed in an M42 adapter, i guess! Inspecting with strong flashlight the front glass has a slight fog, otherwise, with naked eye it is perfect! BTW, the lens is in like new condition both outside and inside, the aperture ring moves like butter, the blades are clean and shiny, with perfect coatings, without dusts inside, etc! I shot a test with it... that is the last pic, without any modification, wide open (at f/4)! It is quite sharp and contrasty enough, I think! And this is the full picture, without crop!