Ok, thank you for your generosity.
I found an article about Panoramica cars by Zagato: there are 13 cars pictured there and the article lists all the ones that received that body.
According to the article, the Panoramica design was used for a Fiat 500b tuned by Facetti (that raced with #67) and a Fiat 500c with a Testadoro engine, nicknamed 'Scansina' with #623.
The Scansina is quite known and I doubt it was never reported that it was the old Drin-Drin, but it's the only guess I can think of.
...and here's another Panoramica by Zagato:
[attachimg=1]
You can unlock, then, I'm afraid I'm running out of time!