There has never been a Montblanc leather line called Meisterstück Prestige. Anyone offered an organiser under that name should therefore not jump to the conclusion that it is a fake, but first suspect a mix-up on the seller's part: what is meant is in all likelihood the Meisterstück Platinum version, which was available with platinum-coloured fittings alongside the classic line with gilt ones. The fact that nothing at all can be found about the supposed name points to precisely this error, not to an especially rare piece.
Price is no test of authenticity with leather goods either. Used organisers lose a great deal against their price when new; a figure of around 120 euros was perfectly plausible in 2013 for a used but well-preserved example. What should be examined instead is the workmanship and the stitching, the embossing of the logo, and the quality of the zip, the ring mechanism and the interior fittings. Counterfeit Montblanc leather goods almost always give themselves away at first glance through coarse or crooked stitching, unevenly finished edges and stiff, cheap-feeling leather, whereas the wrong model name on its own proves nothing.