A mixture of that kind is a sure sign of a fake. The 144 and the 145 are closely related Meisterstück models in the smaller Classique size, but they differ in details such as the nib ring, the section and the design of the thread. Parts from the two models were never mixed at the factory. Anyone finding the ring of one version and the thread of the other on the same pen is looking at a copy that has taken its cues from several originals at once without getting any of them right.
A second and usually still clearer indicator is the nib: on fakes the engraving looks flat and monotonous, whereas the stamping on a genuine nib shows clearly stepped depths and clean edges. With listings of this sort the box and the converter are almost always counterfeit too, so the suspicion can be confirmed on several separate components. Price proves nothing about authenticity: in 2014 a pen like this was being offered at 399 euros, appreciably more than a used 145 normally fetched at the time.