Monte Rosa was Montblanc's budget second brand. A pen engraved “Monte Rosa” along the lower edge of the cap is therefore a genuine product of the Hamburg firm, even though the white star and the Montblanc name are absent. Their absence is how the line was meant to be and is no mark of a fake.
The background: until the late 1980s Montblanc was a full-range supplier making everything from the cheap school pen to the expensive Meisterstück; only from the early 1990s did the company position itself exclusively as a maker of luxury goods. Monte Rosa served the lower price segment, which is why the materials, the finish and the feel in the hand are noticeably plainer than on a Meisterstück of the same date.
In form and engineering the Monte Rosa models are closely related to the simpler Montblanc lines of the 1950s, in particular the 342 and 344 series; comparison with those models will usually place an inherited pen. A black body with a metal cap and a translucent blue ink window for the ink level fits that picture well. The collector's value is slight, but as sturdy everyday pens these are still perfectly serviceable.