i've seen one in person... it can see behind itself! There was a camera store in town 20 years ago that had one attached to an F3 w/sports finder, and a bunch of other nikon gear, nikonos, etc., in a display case that was later crushed by a truck that ran into the store, subsequently a burglary took place that night and among other things in that store, that nikon display and it's contents were gone... nikon didn't just produce these lenses, they would built them to order, so they are rare...
That has got to be the coolest looking camera lens I have ever seen. I don't have 35,000 to spend on a lens, but I still am oddly tempted to hit the BIN
I did some searching on another forum a few days ago and someone posted that they were attempting to buy from a private seller. He reported a few days later that the seller sold the lens, an F3 and some accessories all for $3,000!!!! I would buy that lens in an instant for $3K, just to be able to say I have one, not to mention I could probably retire on the profits in ~50 years.