I have one in M-mount for sale. Its one of the older ones that came optimized for f2.8, so focus is accurate at all apertures from f2.8 to 16. Newer ones came adjusted to be accurate at f1.5, but give inaccurate focus at all other apertures because of the focus shift these lenses all have. The 2.8 version can be adjusted for f1.5 by a repair tech.
Mine is in good condition, with no scratches, cleaning marks, fungus, or haze. Focus is spot on at f2.8 and below on my two M6 bodies. The lubricant in the helicoid has dried up and caused the infamous Zeiss wobble problem. Focusing is not stiff, still moves freely, and it doesn't affect image quality. I bought it used 2 years ago in this condition and it hasn't changed. I have the original Zeiss hood, which looks nearly new, and will include it with the original front cap and a generic rear cap. $950 including shipping and paypal if you're interested.