I've only seen it referenced in print. As you said the car has the normal set up as a regular car with full manual gearbox with the exception of no clutch pedal. And I would assume it was the precursor to the “F1” gearbox. The working description is as you've stated above. But, it was never used in any other car. And as far as how many Mondials it came in I would assume it was a very, very small number. I think it first showed up in the 3.2. So if you have found a Mondial T, a rare bird to start with, that has this transmission you’ve really got a very rare car. How reliable it is… I have no idea. The Ts were as reliable as the early 348s and those weren’t the most reliable Ferraris (we’ll leave it at that- as much as I love them). So, throw in a crazy (did I say crazy? :nuts: ) gearbox and who knows?!
I’d say go take a look at the car and take it for a spin. You’d certainly would be one of the very few who would ever have the experience of driving a car like that.