Thanks for the replies.
The problem is the owner doesn't know what kind of boat it is either.
I saw the boat today. The owner thought it was built in 1980, but looking at the polyester it looks a bit newer, I would say 1990s. I was unable to find an hull identification nr of something like that.
Another problem is the height. Compared to a Centaur that was in the harbour I'd reckon it's about 8 mtrs.
The owner said it might be a french boat, with a non original rigg.
Thanks for the remark about the draft, but it will be no problem on the Buiten IJ.
I'll let you guys know if I find out anything (i'm gonna see if there are any french sailing forums!).