Thanks for the useful data, gentlemen.

ST 480 JK Welding
257-A S 47 Feb-44 US Army ST tug Design 257-A (88 built in design 257 and 257-A)
106 GRT, L22,56m, B6,10m, Dr2,54m (74'x20'x8.4')
steel, 1 scr (3bl.), diesel 2t 6cyl Atlas-Imperial type 6BM, 400bhp @300rpm, sp 9,13kn, bp 6t
ST 480 WARTUG
1944 -xx/03: Launched by "J.K. Welding Co" at Brooklyn, NY.(USA) (YN 73)
1944 -xx/04: delivered to the US Army (USA)
1945: transferred to Rotterdam (NLD)
Post-ww2 Captain was Jo de Biljl.
1946: To the Finnish Govt. (FIN), renamed No 12
1947: To "Österbottens Trä A/B" at Jakobstad (FIN), renamed TOLVAN
1979: To Kalajoen Huolinta at Kalajoki (FIN)
1987: To Mauri Kaarlo Furu at Siilinjärvi (FIN)
ST 480 Tolvan
Byggd 1944 vid J.K.Welding Co, Brooklyn NY
22.70 x 6,26 x 2,90 - 106 brt
Maskin: Atlas Imperial 6 HM, 500 Ehk
Owner since 2008: Bengt Vilhelm Fredriksson
Apparently still has original Atlas Imperial
Engine and other drivetrain parts. Still exists in 2010 but needs restoration.

A WW-II era U.S. Army ST class tug built in the U.S.