Pentacon 2.8/80 Projection lens to Nikon F-mount adapter

This is an big tube adapter to fit on the front of a nikon camera and to screw a Pentacon 80mm ƒ/2.8 projection lens into. Get beautiful soap bubble bokeh for so much less than a trioplan lens.

This is not a generic pentacon mount to f-mount. This is one specific slide projector lens (pentacon 2.8/80 AV) to Nikon f-mount. There may even be different sizes of this one lens. This one had a barrel diameter a little over 51mm (over 2 inches). Might be called a Pentagon XL.

This adapter comes i