I forgot, just reposting as a reply to Gaston's seatpost post :) But yeah, a Demax.
Clearance is tight with 28mm! Not touching though but I did fit some helicopter tape just in case.
It's not for sale currently (I bought it off here ages ago actually). Will drop you a PM when I see one pop up. Out of these last generation steel Gazelles, the Superbe is also a nice frame that appears regularly on Markplaats