On newer Montblanc ink boxes and on the 'shoe' of the ink bottle a white transverse stripe is printed; if this is missing it can be older shelf goods. Ink in principle has a best-before date that can be found on the packaging. In practice, ready-mixed water-based ink stays stable long, provided the bottle is tightly closed; even collectors who have emptied many bottles barely observe real quality losses over the years. Iron-gall inks and chemically more complex types behave differently and can actually oxidise or thicken.