Thank you for the information davidships!
Andi

The tug is WALTERSHOF.

From Piet van Damme's database:

Registered: (DEU)ON B18574
52 GRT, L18,28m, B4,98m, D(2,24)
1 scr, C2cyl by shipbuilder, 225ihp
re-engined 1949 C2cyl (1947) by "Christiansen & Meyer" (nr.1006), 240ihp @170rpm

COLLET
1911 -xx/05: Launched by "Johannes van Bergh" at Delfzijl (NLD)
1911 -14/06: delivered to August E. Peters at Hamburg (DEU)
(DEU flag, regd Hamburg, ON B18574)
1916 -14/07: To "Hugo Stinnes AG" at Hamburg (DEU), renamed HUGO STINNES V
1927 -24/06: To "Hapag - Hamburg Amerika Linie", mng "Lütgens & Reimers" at Hamburg (DEU), renamed EXPERT
1939 -28/09: requisitioned by the German Kriegsmarine (DEU), Bauaufsicht Neptunwerft Rostock
194x: transferred to Marineausrüstungsstelle Warnemünde
1942: transferred to Schlepperbereitschaft Kommandant Hamburg
1945 -08/04: sank in an air raid in the Mittelkanal, Hamburg
1945 -05/12: raised, repaired by "J. Oelkers" at Hamburg (DEU) and returned to owner
1949: rebuilt, lengthened L22,10m, B5,56m, Dr2,57m, re-engined C2cyl (1947) by "Christiansen & Meyer" (nr.1006), 240ihp @170rpm
1949 -02/08: renamed WALTERSHOF
1958 -10/02: To Hans Bonertz at Hamburg (DEU), rebuilt as a tank cleaning vessel, renamed VAMPYR
1961 -24/08: renamed VAMPYR II
1965: boiler replaced (1931)
1989: reported still in service
1995: donated to "Verein Alsterdampfschiffahrt e.V."
2000: restoration started by ""Freundeskreis Dampfschlepper Vampyr e.V."
2002 -xx/02: boiler taken out and sold to Dampfeisbrecher "Elbe" at Hamburg (DEU), re-renamed WALTERSHOF
2011: still in existence