Try a search on "Cooke XVa" and you'll turn up several existing threads on this lens.

When I was considering it, I came to the conclusion that it would make more sense--if I wanted a modern sharp field lens or three for 8x10"--to buy a trio of Fujinon-C lenses (300-450-600) for about the same price new, each being a complete, corrected lens, easy to swap in the field without dealing with the logistics of a convertible. In the end, I decided to stick with my classic lenses (10" WF Ektar, 12" Golden Dagor, 19" Apo-Artar being my main trio of 8x10" lenses, with a few extras on the wide end and portrait lenses for the studio).