I think this was assisting ACT 3 into RDM dockyard to have boiler modifications, reduction of superheater.

DOCKYARD IX
Built: 1943
Builders: RDM - Rotterdamse Droogdok Mij NV., Rotterdam, Netherlands. Yard# 226
Owners: RDM - Rotterdamse Droogdok Mij NV RDM - Rotterdamse Droogdok Mij NV
92 grt.
Dimensions: 25.06 x 6.31 x 2.31 m.
Speed: 9.5 knots.
1 fpp +dir. nozzle, 2x C2cyl (1942) "RDM-Lentz" nr.254 (boiler (1940) "RDM"), coal fired (1961 oil), 82nhp-500ihp @210rpm (with nozzle, 650ihp).
Bollard Pull 8.3t

History.
1940 -26/11: Launched by "RDM - Rotterdamse Droogdok Mij NV" at Rotterdam (NLD) (YN 226)
(originally on USSR order, but never delivered. She made part of a series of 10 but it isn't certain they were all built)
1942 -15/01: completed for "RDM - Rotterdamse Droogdok Mij NV" at Rotterdam (NLD)
1944 -xx/10: requisitioned by the German Kriegsmarine (DEU)
1945: returned to "RDM - Rotterdamse Droogdok Maatschappij" at Rotterdam (NLD)
(NLD flag, regd Rotterdam, brand:9768 B Rott 1956, IVR 23.09768)
1978 -24/08: donated for 1 symbolic guilder to the city of Rotterdam, who transferred it (24/08/1978) to "Maritiem Museum Prins Hendrik" part of "Stichting Buitenmuseaum", Leuvehaven 1, at Rotterdam, maintained and operated by "Stichting Dockyard IX"
1992: after long restoration back in service
1994 (25/05): To "Stichting Buiten Museum" at Rotterdam (NLD)
2012: still in existence

Info from TUGSLIST, created by Piet Van Damme (Belgium).