10 Pfg air-mail with plate error "comma above on the left at the left tower" with additional franking national coat of arms 3 Pfg (10) and 5 Pfg (2) with special postmark " DANZIG/XIXth UNIV. KONGRESO de ESPERANTO, 4.8.27. 14-15 " on a correctly stamped airmail R cover to Berlin with arrival postmark, perfect, certificate Erdwien BPP (1998)