Yes it was the Zenith and its Gradua drive.
I would like to see one and exactly how it worked. From what I have heard so far it had a primary belt and a secondary belt to the rear wheel. Just how the rear wheel could be adjusted for and aft is not too clear. One thing I read was that the primary pulley could be adjusted while in motion but the overall ratios could only be changed by adjusting the position of the rear wheel in the forks.
I suppose it meant that when you arrived at a circuit the bike could be set up for the conditions then the primary pulley could be varied during the race to maintain the optimum engine revs.
Anyone who knows may correct this understanding.
Makes you wonder if one of the current makers came up with a revolutionary transmission would it be barred.