Another view of this vessel shows "772" scrawled on the bridgefront, so I believe this is the DPC 58, later U.S.Army ST 772, which served in the Greek Navy as PERSEUS (A 429), then presumably was transferred to the Port of Piraeus. See photo marked OLK R K 1 dated 14 Aug 09 by Peter J Fitzpatrick.

The tug is not a U.S. Army ST class, she's a DPC (Defense Plant Corporation) class, one of a total of 100 built during WW-II for service towing oil barges in harbors and along the coast.