The Neckar brand is interesting. Essentially, these were Fiats built under license by NSU (see the NSU/Fiat badge up in the top left), but things get weird because there were two NSUs at the same time. One was an NSU factory sold to Fiat as the result of the Great Depression, and the other was the NSU Werke AG plant in Neckarsulm.
Even more confusingly, the Fiat-NSU plant not in Neckarsulm is the one that decided to brand their cars as “Neckar” just so every one stays nice and confused.
That said I sure do like the bold, colorful graphics in this ad, with those ultra-saturated 1950s colors. I don’t think the design has anything to do with that license-built Fiat 1100, but it looks modern and suggest this car must be, too.