The convertible Hitler rode in was a 38, not a 39. This is proven by the fact that the cornerstone laying ceremony was in May 38. That convertible was given to Adolf as a gift, and he sent it to his Austrian retreat in the mountains.
That car has the most interesting history. Post war found it in the hands of an unknown individual, who probably didn't know it was Adolf's car. The guy drove it for many years then traded it in at a VW dealer in the early 50s. The dealer did some restoration on it then put it on the lot and sold it to yet another unsuspecting owner. The guy knew it was really old because in the late 50s when VW put the word out looking for the oldest VW, he came forward. He traded it for a new Karmann cabrio. VW then restored it and placed it in their museum. The car is supposed to have between 2 and 300,000 km on it!