Originally Posted by Field
It just doesn't look like it could cover a 35mm film plane... Maybe I'm wrong. Notice that the overall diameter is nearly half of a regular exakta lens.
There is nothing to accurately reference the diameter of the lens in the photos that you supplied, a hand does not count as hands come in all sizes.
Non auto Lenses for Exakta are not very big and there is a myriad of them by various lens makers, made throughout several decades too.
Almost any lens making firm worth its salt made lenses to fit the 35mm Exakta camera.