CH 1943 W18 Bloc GEPH FDC ill. no address

Switzerland 1943 W (Semi-postals and Special issues sold at an additional premium)
memorial bloc GEPH Geneva (Genf) - National Stamp Exposition, "100 Jahre Schweizerische Postmarken (Doppel-Genf) 1843-1943",
FDC ill. Cover without address, cancelled with red special cancellation "17.IX.43 GENEVE - GEPH Exposition Philatélique Nationale",
rarely without address, Top quality,
Catalog SBK W18, Michel Bl. 10.