U. Nehring Lens Cells --- Does Anyone Have Any Knowledge of These?

I have a set of U. Nehring lens cells in a small padded box. These have no barrel and no shutter but about ten years ago I found a shutter they screwed directly into. Unfortunately, I can't remember what shutter. Anyone know anything about these?

I wonder if they are just supplementary wide angle accessory lenses that screw into the front of a normal lens.

Nope... this is a normal set of vintage lens cells.