...It is a Dutch bike with matching numbers, VIN is s650-025329.
My question is is it a xs-1B or F?
And how should the front fender be attached?
Both attachments are seen on the candy orange bikes. But what is correct for my bike?
Welcome to the forum, Pepijnwk. My VIN is close to yours, S650-0244xx. We both have the later versions of the XS1B and XS1F.
If your bike is a European Dutch bike, then it would be an XS1F.
Both styles of front fender are correct. The front forks may or may not have the optional "Enduro" type lower mount ears. If you have these enduro forks, then either fender type could be used. If not, only the upper brace style fender will work.
The attached pictures are from an early European 70-72 parts manual, and show the different fork/fender options for the XS1F (and XS1B).
For more info, use forum search of "XS1F"...