I´d say this may be a Kässbohrer design.
They´re still known for their buses and this must have been a very rich company, that may have used it for quite exclusive tours.
Mercedes S (620) chassis, ca.1929-1930.
I have found a similar vehicle named "Reiselust" in a book, where it ran for a company "J.Nerbl" from Weilheim in Bavaria.