I would not trust Fusi's data, it's riddled with errors. FIAT offers a service so you can find out the exact day your car was "produced".
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The chassis were assembled at the Pinninfarina plant, placed on dollies and rolled off to a "corner". They sat there until Alfa came and got them. They were trucked to the Alfa assembly plant and inserted in the assembly line to get the mechanical components installed.
Your car could have sat at Pinninfarina for days, weeks or months. There is a serial number stamped onto the boot floor. That is a Pinninfarina internal number, a serial number of sorts. I don't know if anyone has ever approached them to see if records are available.
Does your car have a plastic VIN plate in the driver's door jamb?
There are some Alfas that were manufactured in 1969, but titled as 1970. There are some Alfas that were manufactured in 1970 but titled as 1969. And, there are some Alfas manufactured in 1970 and titled as 1970. If your car has a plate like this and the date is late in the year, I would say there is a chance it is a lie.