Abarth 750 RM 513608
Thank you BoneMaro!
This is all good stuff. Yes, I would say the car was built 1958. I suspect the ledger date was close to the completion date ... as far as Zagato's work was concerned, but again, this is uncertain. The car may very well have been first sold in 1959, but your title/registration paperwork may imply otherwise?
Unfortunately, I did not receive a copy of the original Zagato ledger itself. It is clear that the ledger was not complete in any case. What I received was a dot-matrix printout prepared by Marco Antonetto, a pen-pal friend in Switzerland who was assisting with organizing the Zagato Register (at Zagato) in the early 1990's. We exchanged lots of data but I never received any primary copies. All I have is the data. I may have tossed the dot-matrix printouts after entering the data into my first computer? I entered the data in such a way that the source is recognizable to me.
I have also a photocopy of a handwritten Abarth ledger that appears to describe cars that were given "Certificates of Origin" in Italy. This was done only for cars that were sold for use in Italy. That's not to say that some cars may not have been exported immediately or almost immediately in any case, but the important detail is that your car is not on the list. This implies that the car was exported from new and the most likely destination was the USA, particularly since the car seems to have appeared in California while still almost new ... if not new.
So, on to what you have shared ...
The Abarth ID plate appears likely to be the original. It tells us the Telaio (chassis) number and the Motore (engine) number that was fitted when first sold. The engine with the car now is not the original and dates probably from 1959 or 1960.
The Fiat ID plate has nothing to do with your car as far as its origins go. It seems most likely that the plate is from a Fiat 600 rather than an Abarth variation, but if it were from an Abarth, it would most likely have been a "Double Bubble". If there is anything scratched on the backside, there may be a hint in that? Please check the Abarth ID plate as well, for something that might be scratched there. I am not expecting you to find anything, but you don't know unless you look.
Finding the trim number in three places (and probably more) is a good indication that we are looking at the car that was described as of 1958 in the Zagato ledger.
I will now look to find some additional information to keep you awake wondering ...
John