TZ-2 chassis number 750.104
I spoke to the very enthousiastic (German) owner at the Spettacollo Sportivo happening in Assen and he said it was chassis 750.104.
He found the chassis about 20 years ago in Sicily. The story was that the car had been used as a recce car for the Targa Florio and was bent during testing. The car/wreck stayed behind and that's where he bought the chassis.
He has been buying original and remanufacturing parts and has built up the car over the last couple of years.
In order to get the originality of the chassis established he was having material analysis done.
A picture of the car is in Tony Adriaansens book Allegerita (no pagenumbers) with the registration UD 111645 and the same photo is used in Marcello Minerbi's SZ et TZ book on page 108.
As conclusive / precise records were clearly not kept by Autodelta and Alfa Romeo the truth must come from other sources.