CH 2001 Stamp Day Bern BE, postal card cancelled 7.-9.12.2001 4000 Basel used as a maximum card

Switzerland 2001 Stamp Day Basel BS,
official postal card of Swiss Post (postal stationery)
"Tag der Briefmarke 2001 in Basel - 'Moderne Architektur in Basel' -
Journée du timbre 2001 à  Bâle - 'Architecture moderne à Bâle' -
Giornata del Francobollo 2001 a Basilea - 'Architettura moderna a Basilea'",
with printed franking, without address, cancelled "7.-9.12.2001 4000 Basel - Tag der Briefmarke - BASILEA 2001",
used on the front as a maximum card with a matching special stamp for Stamp Day 2001 (SBK 1038, Michel 1777) , luxury conservation.