In technical museum of Mannheim (Technoseum) I found this interesting dockyard model (scale 1 : 50) of the last built Rhine paddler. The "Mainz" was built 1928 - 1929, 82 meters long,  with compound engine of 900 hp. The boat was in use until 1982, then museum ship in Mannheim.
There is still one Rhine paddler with steam engine in navigation in Netherland: The similar "Majesteit" of 1926, ex Rüdesheim, ex Rheinland.

The "Majesteit" of 1926, 750 hp, compound engine.