The 144 was produced until about 2000; the M label on the pen denotes the nib width Medium but is only present on new instruments. A missing serial number in the Montblanc system is not a definitive indication of a counterfeit, since not all data records are completely captured. Authenticity can be clarified using detailed photos, the original/counterfeit PDF and a boutique enquiry. As ink, any common brand like Pelikan 4001 is suitable; the rumour of clogging through third-party ink does not in practice apply, only Indian ink is to be avoided; some American specialty inks like Noodler's Ink are also discouraged. Pelikan 4001 is water-soluble and can be washed out without problems. On colour change, flush the pen with water until no residues are visible.