The phenomenon arises through corrosion of the base material: on older 144s the ring core is of brass, whose gilding in the cap area is damaged through repeated contact with ink residues and through microscopic damage on closing the cap. Thereby especially acidic (iron-gall) ink attacks the brass; together with the gold it forms a local element that additionally accelerates corrosion. Later versions use stainless steel, which on damaged gilding forms a protective passive layer, which is why the problem hardly still occurs there. Repairs are possible: Montblanc exchanges the front part/grip section within the framework of the service flat rate (typically around 49 to 79 euros including shipping); in warranty cases the exchange has already been handled free of charge.