Why, oh why, did this not go into production!?
(Answer: "There's insufficient perceived market demand for it, Sir | you're fired!" ).
But it might have found a niche market amongst professional users; the Brooks Veriwide
and Envoy Wide Angle
spring to mind. I would really have liked to have one of these, had they gone into production.
As it is, I have had to make a cruder functional near-equivalent from a bakelite camera and f/6.8 65mm Angulon.
ANGULON BAKELITE CAMERA SPECIAL - View 1
, on Flickr
Additional: After reading the lens information given in the OP's link ...
It's interesting to compare the 64mm f/6.8 Taylor-Hobson Envoy with the Ultragon. According to the Lens Vade Mecum
the Envoy is 4-glass gauss design. It is tiny, like the Ultragon, but instead of being around a Size "000" (?) shutter, the Envoy is a module with its own aperture iris, and sits forward of the shutter blades in a Size 0 shutter (it is found with Epsilon, Compur(/Rapid), Prontor, Agifold... shutters). The rear of the Size 0 shutter is machined down as far as possible to minimise vignetting. The Envoy has much less aberration at the edges than the (older) Angulon 65mm f/6.8 design (I have both).