Plovdiv-Filibe : 1857-63ca, Telegraph envelope sent to the Head Official of Plovdiv, with reverse showing extremely rare bilingual negative “ADMion TELEGque IMP./PHILIPPOPOLIS = FILIBE TELEGRAFHANE 74 (1857)” negative seal in green. Unrecorded by any catalogue “the only recorded envelope with this seal”. Certificate Nakri (2005)