I haven't found much about the boat, no photos without violating copyrights, but some data.
Schwan I was built in 1897 at Tecklenburg shipyard and sold in 1906.
Schwan II was built in 1907 at Neptun Werft in Rostock for Argo shipping company. In 1938 the boat was converted to blockade breaker #31 "Pinguin" at HDW.
1948: SS Weltonwold, Atkinson & Prickett Ltd, Hull
1949: SS Rhineland, Currie Line, Leith
1956: SS Herriesbrook, Smith's Coasters Ltd, Durban
1957: SS Inyoni, Smith's Coasters Ltd, Durban
wrecked 1962 in South Africa
Data from: Peter Arndt, Deutsche Sperrbrecher 1914-1945
The book shows two photos of the boat in camouflage and under weapons.
Kind regards
Matt