Souvenir sheet issue \"1. Danziger Country\'s postal stamps exhibition, cancelled by rare red special cancel \"Gdansk DAPOSTA 1937 1. DANZIGER NATIONAL POSTAGE STAMP EXHIBITION -8.6.37.-21 6.-8.6.37\", faultless condition, unsigned, photo expertize Gunnar Gruber BPP (2023) \"genuine and in perfect quality. \" - souvenir sheets with red special cancel are extremely rare!