A method and a system is disclosed for affixing invisible or unobtrusive
markings to mail pieces (4), and subsequently collecting information from
the mail pieces for sorting purposes. The system includes the affixation
of an optically contrasting layer (1) to a mail piece, the layer changing
optically upon the application of a stimulus to present a contrasting
background for imaging encoded information (3) applied over the layer and
related to the mail piece.
