Three points separate the original from the copy. On a vermeil version the cap rings are gold-plated as well; rings left silver on a pen that is supposedly gilded do not belong. The 144 in vermeil has an 18-carat nib, not the 14-carat one of the plain model. And on the original the word Pix beneath the clip stands proud, never stamped into the surface.
Apart from these details, such a counterfeit was hardly to be distinguished from an original, all the more so in poor listing photographs. If the cap rings, the nib engraving and the area under the clip are not sharply shown, insist on better pictures before buying.