Won't necessarily claim it to be rare, but I've never seen another Magneet before or since. Given to me by Poguemahone back in '04, I turned it into my long term touring bike. Originally, it was a standard pre-Bike Boom 10-speed: Gaspipe tubing, Campagnolo Valentino drivetrain, Universal center pulls, cottered crank, steel rims on low flange three piece huts and wing nuts. The picture is it's earliest incarnation after I put it back on the road. At this point the frame, headset, stem, bars, dork disk and crankset were still original. As of today, we're down to the frame, headset, stem, and dork disk. And it's a wonderful touring bike.
From what I've learned, the marque was owned by Batavus, which finally discontinued the brand in 1969.