1937, 43. German philatelists day 22. 23. May in Kassel, 3 Pf. Hindenburg postal stationery (with horizontal white line by which design of the stamp) and additional franking Michel no. 513, thickly box, matching special cancellation Kassel 23. 5. 1937, addressed to Bad Nauheim, reverse old KABE printed form part of the Netherlands with 2 old hinge traces as well carmine red senders mark. Whether this a trial printing or a poster section is, over it is you be not yet United, however is this from of this issue down to the present day the only known copy in perfect condition, RRR!