<KBWZ Germany 1991, Michel-No. 1522-25 with special cancellation BONN 1991, April 9th: "Historical Air Mail Transport" Four top right corner edges with additional corrected value prints (KBWZ) complete: "7,50", "12,50", "25,00" und "41,25" D-Mark. Stamps in perfect condition with full gum, not folded. Authenticity warranty. Rarely offered!