None of the three features works as a test of authenticity. Montblanc introduced serial numbers only in the early to mid-1990s; older pens carry none. The “Pix” marking on the back of the clip is likewise found on only part of the production — of two indisputably genuine examples of the same model, one may have it and the other not. And on the 144 the model number is never on the cap ring: alongside the words “Montblanc – Meisterstück” there is simply no room for it. On larger models such as the 149 the number is there, whereas on the matching ballpoints such as the 161 it often is not.
The 144 is among the most frequently faked Meisterstück models, but the nib is what decides the matter: nobody has yet managed a convincing copy of a Montblanc nib. Typical fake nibs give themselves away with markings such as “Iridium point”, which Montblanc does not use.
Two practical points for older pens: hairline cracks in the cap top are a common age-related fault, and used original cap crowns could be had for a few euros (as at 2007). And for unscrewing and refitting the cap crown, the best tool is a piece of PVC tubing about five centimetres long with a seven-millimetre bore; it grips cleanly and transmits enough force without damaging the cap top.