10 on 20 Pfg. Prussian-blue in the unperforated center piece 1 with overprint types combination "Ia / Z / IIs IIIa / Z / IVa" on postage exceeding tariff rate local letter from Opole 15. 3. 20 in perfect in outstanding quality with appropriate certificate with photograph Gruber BPP: ". . . . Is an unique"! - an exhibit for the large collection!