I agree, Michael. Perhaps someone should put up a link to the original S76 FIAT query thread. As you say, many people with very good original sources have countered any suggestions of what it might be. Again like you, and having studied it and photographed it copiously at the FoS, I stand in awe at the level of work and detail which has gone into this device. Similarly, I am a great champion of DP's mechanical skills, both here and with his other cars, and I spent a long time at the FoS listening to the to the Italian engineer who did much of the precision work, a joy to listen to.
I have said before that I look forward to DP showing photographs of exactly what it was that he bought/brought from Australia. Perhaps the film in 2015 will show it all. I always believe sight of what you start with invariably gives the measure of just what you have, and what you have achieved in the restoration. DP is quite clear about what FIAT have supplied in parts and drawings.
Nevertheless, it is a remarkable device, beautifully executed and the only chance I will ever have of seeing one.
Roger Lund