CH 1971 W44 NABA Basel stamp out of bloc FDC ill. with address

Switzerland 1971 W (Semi-postals and Special issues sold at an additional premium)
memorial bloc NABA Basel (National Stamp Exhibition1971),
single stamp out of bloc with matching special stamp on ill. R-FDC (format C6) with address,
cancelled "11.3.71 3000 Bern - Ausgabetag", luxury quality,
no sale in this form by postal administration!
Catalog SBK W44, Michel 946.