Posted by Klaus on February 15, 2001 at 08:03:55:
The French 6-valve trombone by Sax represents another way of distributing the lengths of valve crooks.
Each valve crook is intended to correspond to the positions 2 through 7, respectively, of the slide trombone. The valves were not intended to be used in combinations.
I read about this now obsolete instrument many years ago, but saw no illustrations until last night at the site linked below.
Scroll down that page to find the "master" of 8 pictures.
Klaus