This is the famous "Eight Element Summicron" for the M3 with the goggles. It works on the other cameras and brings up the 50mm frame lines but shrinks the image for a correct view. Ken Rockwell prefers this version, as the smaller view makes it easier to see the full image (and the lens is less expensive than the non-goggles one).
The lens is in excellent condition and works perfectly. The glass is clean and scratch-free with no haze nor fungus.
The focus and aperture are smooth.
There is oil on the aperture but it has no effect on use.
There is an ID number subtly engraved on the back (see photos).