The ring engraving Masterpiece in place of Meisterstück marks an export model: for sale outside the German-speaking countries the model name was translated. A 144 with this engraving and the model number stamped on the piston knob at the rear dates from the 1950s and is therefore a genuine third-series pen.
A painted-on star, by contrast, argues clearly against authenticity. Into the 1950s, Montblanc pens of this series carried no inlaid, solid star in the cap top, but merely the engraved outline of a star, which was never filled in with colour or painted. Where a star has simply been painted on, the pen is a fake.
A missing number on the clip ring, however, is nothing to worry about. Clip ring numbers were introduced only later; older Montblanc pens simply do not have them and are no less genuine for it. As a test of authenticity this feature is consequently of use only for pens made after it was introduced.