Tug [b]T/G Atlas-I[/b] seen in Astypalaia, Greece on 10.07.2007
The former name [b]ΠΡΩΤΕΥΣ[/b] = Proteus and homeport Piraeus is visible on the stern.
So this might be this tug:

IMO number : 5286116
Name of ship : AGIA IRINI
Call Sign : SV4255
Gross tonnage : 147
Type of ship : Tug
Year of build : 1953
Flag : Greece
Status of ship : In Service
Length : 25,72m
Beam : 6,92m
Draught : 3,25m
Engine : 1 scr, diesel, 1500bhp
Speed: 12kn
Built as: PROVENCAL 12
History: 1953: delivered to "Société Provençale de Remorquage SA" at Marseille (FRA)
1954 -18/09: registered (FRA flag, regd Marseille, brevet:73.537, c/s TKLC)
1977: To "Maritime Towing & Salvage" at Piraeus (GRC), renamed PROTEUS
1995: sold and renamed AGIA IRINI
Thanks to Hans and Helmut :-)
Any more information very welcome :-?