It's realy strange. The one site tells that Rotterdam is the port of register, another site tells it's Panam...
OK, my new answer is:
PanamaHere: http://www.fairmount.nl/page.php?idObject=411 (http://www.fairmount.nl/page.php?idObject=411)
and here: http://www.vesseltracker.com/de/Ships/Fairmount-Sherpa-9315563.html (http://www.vesseltracker.com/de/Ships/Fairmount-Sherpa-9315563.html)