1960 / 90, extensive collection of letters with ZKD (Central Committee for State Security) delivery slips, including precursor items, sender franking marks, 15 letters with delivery slips from the 1st issue, 14 examples from the 2nd issue or delivery slips for VVB (Main Departments), 7 letters with stickers for confidential official mail (Michel D1) and 3 examples with sticker Michel D2, 6 examples with service stamps for shipments with proof of delivery (Michel E1) and many other interesting items, ZKD stickers, ZKD flag, control stamps, etc., a total of over 140 letters, most of the letters examined by Weigelt BPP / Engel. An unusual item, carefully collected over many years of philatelic activity, Michel value approximately 6000,-Euro.