The guy I bought this from claims he was on a camera crew for the hit TV show and that it was actually used for some of the shooting for wide angle shots.
Hey, with a history like that, I wanted to have it!

The lens gives a full 180 degree view when attached to the front of a primary lens.

I had some work to do on it when I got it in the mail... the rear adapters, including the Series VII to 52mm adapter, were all frozen in place and would not unscrew.
And the little rear cap was also frozen, would not budge. I drilled two holes in it and tried to remove the cap with one of my best lens spanner tools. I gave it force until a tip of my tool snapped off.
So my answer was to use a good quality 3/4 inch twist drill to make a hole through the aluminum of the cap, about the size of the cap opening.

For my test today I mounted the device to the front of a manual focus f:2.8 / 28mm lens with 52mm filter size, and put it all on my Pentax K-10 D body.
Exposure had to be adjusted about a stop in the software, and the circle of image cropped from the full frame.

Any future testing would involve trying different length prime lenses, and exposure bracketing.

Please click on thumbnails to see enlarged.
All images are (c) 2017 E.J.Kowalski.
Thanks! Ed