1855 - 20c deep blue, 1st plate, printing of 1859,

 1855 - 20c deep blue, 1st plate, printing of 1859, from 'MILANO 28 DIC 59' to Casale. An extremely rare cover sent from the 'Istituto dei Ciechi' in Milan, written using a special device producing text in dotted characters, predating the later system devised and introduced by Louis Braille. The earliest recorded document with embossed dotted writing for the blind transmitted through the mail. A major rarity. Detailed certificate E.Diena (Sassone 15B – Euro –)